National Study of Mental Health and Wellbeing methodology

Non-sampling error is caused by factors other than those related to sample selection. It is any factor that results in the data values not accurately reflecting the true value of the population.

It can occur at any stage throughout the survey process. Examples include:

• selected people who do not respond (e.g., refusals, non-contact)
• questions being misunderstood
• responses being incorrectly recorded
• errors in coding or processing the survey data.

Sampling error is the expected difference that can occur between the published estimates and the value that would have been produced if the entire population had been surveyed. Sampling error is the result of random variation and can be estimated using measures of variance in the data.

One measure of sampling error is the standard error (SE). There are about two chances in three that an estimate will differ by less than one SE from the figure that would have been obtained if the entire population had been included. There are about 19 chances in 20 that an estimate will differ by less than two SEs.

A confidence interval expresses the sampling error as a range in which the population value is expected to lie at a given level of confidence. A confidence interval is calculated by taking the estimate plus or minus the MOE of that estimate. In other terms, the 95% confidence interval is the estimate +/- MOE.

A panic attack is a discrete episode of intense fear or discomfort that starts abruptly and peaks within a few minutes. Panic attacks last at least some minutes but typically less than half an hour. At least four symptoms must be present from the list below, one of which must be from the first four:

• pounding heart
• sweating
• trembling or shaking
• dry mouth
• difficulty breathing
• feeling of choking
• chest pain or discomfort
• nausea or abdominal distress
• dizziness or light-headed
• feelings of unreality or depersonalisation
• fear of passing out or losing control
• fear of dying
• hot flushes or cold chills
• numbness or tingling sensations.

The essential feature of Panic Disorder is recurrent attacks of severe anxiety (panic), which are not restricted to any particular situation or set of circumstances (i.e., do not occur in the presence of a phobia, or in situations of danger) and are therefore unpredictable.

Characterised by marked and consistently manifest fear in, or avoidance of, at least two of the following situations:

• crowds
• public places (i.e., using public transport; standing in a line in a public place; being in a department store, shopping centre, or supermarket; being in a movie theatre auditorium, lecture hall, or church; being in a restaurant or any other public place)
• travelling alone (i.e., travelling alone or being alone away from home)
• travelling away from home.

At least two of the following anxiety symptoms must have been present together with the feared situation and one of these symptoms must be from the first four listed:

• pounding heart
• sweating
• trembling or shaking
• dry mouth
• difficulty breathing
• feeling of choking
• chest pain or discomfort
• nausea or abdominal distress
• feeling dizzy or light-headed
• feelings of unreality or depersonalisation
• fear of passing out, or losing control
• fear of dying
• hot flushes or cold chills
• numbness or tingling sensations.

The person also experiences significant emotional distress due to the avoidance or the anxiety symptoms and recognises that these are excessive or unreasonable.

Characterised by fear and/or avoidance of one or more social or performance situations such as:

• meeting new people
• talking to people in authority
• speaking up in a meeting or class
• going to social gatherings
• performing in front of an audience
• taking an important exam
• working while someone watches
• entering a room when others are present
• talking with people they do not know very well
• disagreeing with people
• writing, eating, or drinking while someone watches
• using a public bathroom
• dating
• social or performance situation.

The presence of Social Phobia is also characterised by:

• The fear of being the focus of attention or of behaving in a way that will be embarrassing or humiliating; or the avoidance of either being the focus of attention, or of situations where there is fear of behaving in an embarrassing or humiliating way
• At least two anxiety symptoms (from the list in Agoraphobia above) must be present in the feared situation at some time since the onset of the disorder, together with at least one of the following: blushing or shaking; nausea or fear of vomiting; or the urgency or fear of losing control of bowels or bladder
• Significant distress caused by the symptoms or by the avoidance, and the person recognises that these are excessive or unreasonable.

Characterised by a period of at least six months with tension, worry and apprehension about everyday events and problems. The disorder is not due to a physical disorder or substance use. At least four of the following symptoms must be present, with at least one of the first four:　

• pounding heart
• sweating
• trembling or shaking
• dry mouth
• difficulty breathing
• feeling of choking
• chest pain
• nausea, stomach pain or discomfort
• dizziness
• feelings of unreality or depersonalisation
• fear of losing control or passing out
• fear of dying
• hot flushes or cold chills
• numbness or tingling sensations
• muscle tension or aches and pains
• restlessness
• feeling on edge
• a sensation of a lump in the throat
• exaggerated response to minor surprises
• difficulty concentrating
• irritability
• trouble in getting to sleep because of worry.

Hierarchy rules have been applied to Generalised Anxiety Disorder. To meet criteria for the 'with hierarchy' version:　

• the Generalised Anxiety Disorder does not occur exclusively within the duration of Panic Disorder
• the Generalised Anxiety Disorder is not exclusively associated with social and performance situations (i.e., Social Phobia)
• the Generalised Anxiety Disorder does not occur exclusively within the duration of (and is not exclusively associated with) obsessions and compulsions (i.e., Obsessive-Compulsive Disorder).

The original exclusion rules from the ICD-10 also consider the presence of other phobic disorders and hypochondriacal disorder. As the 2020-21 study did not collect information for Specific Phobia or Hypochondriacal Disorder, the Generalised Anxiety Disorder prevalence may include some people with these disorders.

Either obsessions or compulsions (or both) are present on most days for at least two weeks. Obsessions (thoughts, ideas, or images) and compulsions (acts) share the following features, all of which must be present:　

• repetitive and unpleasant, and at least one obsession or compulsion is acknowledged as excessive or unreasonable
• the person tries to resist them, and at least one obsession or compulsion that is unsuccessfully resisted must be present
• the person derives no pleasure from the obsessive thought or compulsive act
• the obsessions or compulsions cause distress or interfere with the person's social or individual functioning
• the respondent considers that the obsessions and compulsions do not occur exclusively within episodes of depression (i.e., this is based on self report by the respondent, not according to diagnosis made by the WMH-CIDI 3.0).

Characterised by symptoms experienced within six months of exposure to a traumatic event which would be likely to cause pervasive distress in almost anyone. To be assessed for this disorder, the respondent had to have reported experiencing at least one of the following traumatic events:

• direct combat experience in a war
• a war or ongoing terror as a peacekeeper
• a war as an unarmed civilian
• living in a place with ongoing terror
• ever being a refugee
• being kidnapped or held captive
• being exposed to a toxic substance
• a life-threatening car accident
• a life-threatening accident
• a bushfire, flood, or other natural disaster
• a man-made disaster or bomb explosion
• a life-threatening illness
• being beaten as a child
• being beaten by a spouse or partner
• being beaten by anyone else
• being mugged, held up or threatened with a weapon
• rape
• sexual molestation
• being stalked
• an unexpected death at a young age of someone very close
• a child with a life-threatening illness or injury
• traumatic experience (e.g., kidnap, torture, or rape) of someone very close
• witness serious physical fights at home as a child
• someone being badly injured or killed, or unexpectedly seeing a dead body
• doing something that accidentally led to serious injury or death of another person
• seriously injuring, torturing, or killing another person on purpose
• witnessing atrocities
• any other extremely traumatic or life-threatening events
• any other extremely traumatic or life-threatening events including events the respondent does not wish to describe.

The respondent was asked to determine which event was their worst traumatic event. To meet the criteria for this disorder, the person must report all the following reactions to their worst traumatic event:　

• The traumatic event is persistently remembered or relived (e.g., flashbacks, dreams, or distress when reminded of the event), or the person experiences distress when exposed to circumstances resembling or associated with the event
• The person exhibits an actual or preferred avoidance of circumstances resembling or associated with the event, which was not present before that event
• The person exhibits either an inability to recall some or all aspects of the trauma or two or more symptoms of increased sensitivity and arousal (difficulty in falling or staying asleep; irritability; difficulty concentrating; hypervigilance; exaggerated startle response).

Hypomania is characterised by elevated or irritable mood to a degree that is abnormal for the individual concerned and sustained for at least four consecutive days. It leads to some interference with daily living but to a lesser degree than Mania. At least three of the following symptoms must be present:

• increased activity or restlessness
• increased talkativeness
• distractibility
• decreased need for sleep
• increased sexual energy
• overspending or other types of reckless or irresponsible behaviour
• over-familiarity or increased sociability.

Hierarchy rules have been applied to Hypomania. To meet criteria for the 'with hierarchy' version, the person cannot have met criteria for an episode of Mania in their lifetime. If they do meet criteria for Mania, the duration of Mania and Hypomania cannot overlap (Mania onset must be after Hypomania recency or Hypomania onset must be after Mania recency), or the longest Hypomanic episode must have been longer than the Manic episode.

The original exclusion rules from the ICD-10 also consider the presence of any Depressive Episodes, Cyclothymia and Anorexia Nervosa. As the 2020-21 study did not collect information for Cyclothymia or Anorexia Nervosa (and the presence of Depressive Episodes was not operationalised by the diagnostic algorithm), Hypomania may include some people with these disorders.

Mood is elevated, expansive or irritable and abnormal for the person concerned. The episode lasts for at least seven days (unless the episode is severe enough to require hospitalisation), causes severe interference with personal functioning, is not directly caused by substance use or a physical condition, and is characterised by at least three of the following (four if the mood is merely irritable):

• increased activity or restlessness
• increased talkativeness
• flight of ideas or the feeling that thoughts are racing
• loss of normal social inhibitions
• decreased need for sleep
• inflated self-esteem or grandiosity
• distractibility
• reckless behaviour
• marked sexual energy or sexual indiscretions.

Depressive Episode lasts for at least two weeks and is characterised by the presence of a number of the following symptoms:

• depressed mood
• loss of interest in activities
• lack of energy or increased fatigue
• loss of confidence or self esteem
• feelings of self-reproach or excessive guilt
• thoughts of death or suicide, or suicide attempts
• diminished ability to concentrate, think or make decisions
• change in psychomotor activity (agitation or retardation)
• sleep disturbance
• change in appetite.

The study collected information to differentiate between three different types of Depressive Episode, based on the number of symptoms the person experienced:

• Severe Depressive Episode – the first three symptoms from the above list and additional symptoms from the remainder of the list to give a total of at least eight
• Moderate Depressive Episode - at least two of the first three symptoms from the above list and additional symptoms from the remainder of the list to give a total of at least six
• Mild Depressive Episode - at least two of the first three symptoms from the above list and additional symptoms from the remainder of the list to give a total of at least four.

Hierarchy rules have been applied to each of the Depressive Episodes. To meet criteria for the 'with hierarchy' versions, the person cannot have met criteria for either Hypomanic or Manic episodes in their lifetime.

The three types of Depressive Episode collected by the 2020-21 study are also mutually exclusive. A person cannot be diagnosed with Moderate Depressive Episode if the criteria for a Severe Depressive Episode have already been met and a diagnosis of a Mild Depressive Episode is considered only when the other two types of depression have been excluded. This criterion is applied regardless of whether the 'with hierarchy' or 'without hierarchy' versions of the disorder is used.

A disorder characterised by at least two years of constant (or constantly recurring) chronic depressed mood, where intervening periods of normal mood rarely last for longer than a few weeks.

During some of the periods of depression at least three of the following are present:

• reduced energy or activity
• insomnia
• loss of self-confidence or feeling inadequate
• difficulty in concentrating
• frequent tearfulness
• loss of interest in or enjoyment of sex and other pleasurable activities
• feeling of hopelessness or despair
• feeling unable to cope with everyday responsibilities
• pessimism about the future or brooding over the past
• social withdrawal
• reduced talkativeness.

Hierarchy rules have been applied to Dysthymia. To meet criteria for the 'with hierarchy' version:

• the person must not have met criteria for either Hypomanic or Manic episodes in their lifetime
• there must be no episodes of Severe or Moderate Depression identified within the first two years of Dysthymia.

Characterised by episodes of Mania and/or Hypomania either alone or in conjunction with Depressive Episodes. For the 2020-21 study, a diagnosis of Bipolar Affective Disorder was given if the person met criteria for Mania or Hypomania and had experienced one episode of mood disturbance (Mania, Hypomania or Depression). The study does not allow differentiation according to the type of the current episode.

There is clear evidence that the use of alcohol was responsible for (or substantially contributed to) physical or psychological harm, including impaired judgement or dysfunctional behaviour which may lead to disability or have adverse consequences for interpersonal relationships.

The nature of the harm should be clearly identifiable by including at least one of the following:

• frequent interference with work or other responsibilities
• causing arguments or other serious problems with family, friends, neighbours, or co-workers
• jeopardising safety because of alcohol use
• being arrested or stopped by police for drunk driving or drunk behaviour.

Hierarchy rules have been applied to Alcohol Harmful Use. To meet criteria for the 'with hierarchy' version, a person cannot have met a diagnosis of Alcohol Dependence during the same time period (i.e., the duration of the two disorders must not overlap).

A maladaptive pattern of behaviour in which the use of alcohol takes on a much higher priority for a person than other behaviours that once had greater value. The central characteristic is the strong, sometimes overpowering, desire to consume alcohol despite significant alcohol-related problems. A diagnosis was achieved if three or more of the following occurred within the same year:

• strong desire or compulsion to consume alcohol
• difficulties in controlling alcohol consumption behaviour
• withdrawal symptoms (e.g., fatigue, headaches, diarrhea, the shakes, or emotional problems)
• tolerance to alcohol (e.g., needing to drink a larger amount for the same effect)
• neglect of alternative interests because of alcohol use
• continued use despite knowing it is causing significant problems.

The study collected information on:

• Harmful Use - opioids
• Harmful Use - cannabinoids
• Harmful Use - sedatives
• Harmful Use – stimulants.

There is clear evidence that the use of opioids/cannabinoids/sedatives/stimulants were responsible for (or substantially contributed to) physical or psychological harm, including impaired judgement or dysfunctional behaviour which may lead to disability or have adverse consequences for interpersonal relationships.

The nature of the harm should be clearly identifiable by including at least one of the following:

• frequent interference with work or other responsibilities
• causing arguments or other serious problems with family, friends, neighbours, or co-workers
• jeopardising safety because of substance use
• being arrested or stopped by police for driving while intoxicated or other behaviour while intoxicated. 　

Hierarchy rules have been applied to Other Substance Harmful Use. To meet criteria for the 'with hierarchy' versions, a person cannot have met a diagnosis of Dependence on the same substance during the same time period (i.e., the duration of the two disorders must not overlap).

The study collected information on:

• Dependence Syndrome - opioids
• Dependence Syndrome - cannabinoids
• Dependence Syndrome - sedatives
• Dependence Syndrome - stimulants.

Opioids/cannabinoids/sedatives/stimulants Dependence Syndrome is a maladaptive pattern of substance use in which the use of the substance takes on a much higher priority for a person than other behaviours that once had greater value. The central characteristic is the strong, sometimes overpowering, desire to take the substance despite significant substance-related problems. Diagnoses were achieved if three or more of the following occurred in the 12 months prior to interview:

• strong desire or compulsion to take the substance
• difficulties in controlling substance-taking behaviour
• withdrawal symptoms (e.g., fatigue, headaches, diarrhoea, the shakes, or emotional problems) 　
• tolerance to the drug (e.g., needing to use a larger amount for the same effect)
• neglect of alternative interests because of substance use
• continued use despite knowing it is causing significant problems.

The essential feature of this disorder is recurrent panic (anxiety) attacks that occur suddenly and unpredictably. At least one of the attacks has been followed by one month or more of at least one of the following:

• concern about having additional attacks
• worry that the attack means that the person is 'going crazy', losing control or having a heart attack
• change in behaviour because of the attacks.

A person may have met criteria for Panic Disorder with or without the presence of Agoraphobia.

A period of intense fear or discomfort which begins suddenly and reaches a peak within ten minutes. At least four of the following symptoms are present:

• pounding heart
• sweating
• trembling or shaking
• shortness of breath
• feeling of choking
• chest pain
• nausea
• dizziness
• feelings of unreality
• fear of losing control
• fear of dying
• numbness or tingling sensations
• hot flushes or cold chills.

The disorder is characterised by anxiety about being in situations from which escape might be difficult (or embarrassing) or in which help may not be available if the person has a panic attack. Such situations include:

• being outside the home alone
• being in a crowd
• travelling in trains, buses, or cars
• being in a public place.

The person avoids the situations, endures them with distress or requires the presence of a companion.

The symptoms of Agoraphobia relate to a fear of developing panic-like symptoms, but the person has never met the criteria for Panic Disorder.

The disorder is characterised by a marked and persistent fear of one or more social or performance situations in which a person is exposed to unfamiliar people or to possible scrutiny by others. The person fears that they will act in a way (or show anxiety symptoms) that will be embarrassing or humiliating. Exposure to the feared situation almost always provokes anxiety which may take the form of a panic attack. The feared situations are avoided or endured with distress and the person recognises that the fear is excessive or unreasonable. The disorder is accompanied by clinically significant distress and interference with normal routine and functioning.

The duration of the symptoms must have been at least six months for people who were aged less than 18 years when the symptoms last occurred. The duration of the symptoms must have been more than one year or people who were aged at least 18 years when the symptoms last occurred.

The disorder is characterised by excessive anxiety and worry about a number of events or activities, occurring more days than not for at least six months. Three or more of the following symptoms are present (with at least some present for more days than not for the six months prior to interview):

• restlessness
• fatigue
• difficulty concentrating
• irritability
• muscle tension
• sleep disturbance.

The person finds it difficult to control the worry, and it causes clinically significant distress or impairment in social, occupational, or other key areas of functioning.

A person is excluded from diagnosis if the GAD is associated with one or more of the following self-reported conditions:

• mental health
• substance use
• social phobias
• agoraphobia
• specific phobias
• obsessions
• compulsions
• being away from home or apart from loved ones.

Hierarchy rules have been applied to GAD. To meet criteria for the 'with hierarchy' version, the symptoms/disturbance cannot have occurred exclusively during a mood disorder (Major or Minor Depressive Disorder, Dysthymia or Mania).

The disorder is characterised by obsessions, compulsions, or a combination of both.

Obsessions are defined by the following:

• recurrent and persistent thoughts, impulses, or images that are experienced as intrusive and inappropriate and that cause marked anxiety
• the thoughts, impulses or images are not simply excessive worries about real-life problems
• the person tries to ignore or suppress such thoughts, impulses, or images or to neutralise them with some thought or action
• the person realises that the thoughts, impulses, or images come from his or her own mind and are not imposed from without.

Compulsions are defined by the following:

• repetitive behaviours or mental acts that the person feels driven to perform in response to an obsession
• the behaviours or mental acts are aimed at preventing or reducing distress or some dreaded event or situation but are not realistic or are clearly excessive.

The disorder is also characterised by the obsessions or compulsions causing marked distress, being time consuming, or significantly interfering with the person's normal routine or functioning.

Additionally, the person realises that the obsessions or compulsions are excessive or unreasonable.

The obsessions or compulsions cannot occur exclusively within episodes of depression. In this case, depression was based on the endorsement of questions about being sad or depressed when the symptoms of OCD occurred. Therefore, depression was self-reported and not verified medically or through a WMH-CIDI 3.0 diagnosis.

The disorder is characterised by symptoms lasting more than one month following exposure to a traumatic event in which the person experienced or witnessed an event that involved actual or threatened death or serious injury, or a threat to the physical integrity of self or others.

The person's response to the event involved intense fear, helplessness, or horror. The traumatic event is persistently re-experienced in one or more of the following ways:

• recollections
• dreams
• acting or feeling as if the event were recurring
• distress when reminded of the event
• physiological reactivity when reminded of the event.

In addition, the person exhibits avoidance of things associated with the event evidenced by three or more of the following:

• efforts to avoid thinking, feeling, or talking about the event
• efforts to avoid activities, places or people that arouse recollections of the event
• inability to recall aspects of the trauma
• diminished interest or participation in significant events
• feelings of estrangement from others
• restricted range of affect (e.g., unable to have loving feelings)
• sense of a foreshortened future.

Further, two or more of the following symptoms of increased arousal are present:

• difficulty falling or staying asleep
• irritability
• difficulty concentrating
• hypervigilance
• exaggerated startle response.

The disturbance causes clinically significant distress or impairment in social, occupational, and other important areas of functioning.

This disorder is characterised by the presence of five or more symptoms during the same two-week period, with at least one of the symptoms from the first two on the list:

• depressed mood
• loss of interest and pleasure
• weight change or appetite disturbance
• sleep disturbance
• psychomotor changes
• low energy
• feelings of worthlessness or guilt
• poor concentration or difficulty making decisions
• recurrent thoughts of death or suicidal ideation, plans or attempts.

These symptoms must represent a change from previous functioning and are not better accounted for by bereavement. If the depressive episode is associated with bereavement, then the episode must be longer than two months duration. In addition, the episode must be accompanied by clinically significant distress or impairment in social, occupational, or other key areas of functioning.

To be diagnosed with Major Depressive Disorder a person must have met criteria for a single Major Depressive Episode. Hierarchy rules have been applied to Major Depressive Disorder. For the 'with hierarchy' version, a diagnosis can only be made if a person has never met criteria for a Hypomanic or Manic Episode.

Minor Depressive Disorder is diagnosed if a person has at least two (but less than five) symptoms of a Major Depressive Episode. Hierarchy rules have been applied to Minor Depressive Disorder. For the 'with hierarchy' version, a diagnosis can only be made if a person has never:

• met criteria for Major Depressive Episode and Dysthymia; and
• experienced a Hypomanic or Manic Episode.

This disorder is characterised by the presence of symptoms lasting at least two days, but less than two weeks. The symptoms occur at least once a month for 12 consecutive months and are not associated with the menstrual cycle. The symptoms cause significant distress or impairment in social, occupational, or other areas of functioning. At least five of the following symptoms must be present and at least one of the symptoms should be from the first two on the list:

• depressed mood
• loss of interest or pleasure
• significant weight loss when not dieting or weight gain, or decrease or increase in appetite
• insomnia or hypersomnia
• psychomotor agitation or retardation
• fatigue or loss of energy
• feelings of worthlessness or excessive or inappropriate guilt (which may be delusional)
• diminished ability to think or concentrate, or indecisiveness
• recurrent thoughts of death (not just fear of dying), recurrent suicidal ideation without a specific plan, or a suicide attempt or a specific suicide plan.

The symptoms are not better accounted for by bereavement, or if the symptoms are associated with bereavement, they have persisted for longer than two months.

Hierarchy rules have been applied to Recurrent Brief Depression. For the 'with hierarchy' version, a diagnosis can only be made if a person has never had a Depressive Episode and met criteria for Dysthymic Disorder; and had a Manic Episode, Mixed Episode or Hypomanic Episode and met criteria for Cyclothymic Disorder.

As the 2020-21 study did not collect information on Mixed Episode or Cyclothymic Disorder, Recurrent Brief Depression may include some people with these disorders.

The disorder is characterised by a chronically depressed mood, which occurs for most of the day and on more days than not, for at least two years. There cannot have been a break of two months or more. Additionally, at least two of the following symptoms are present:

• appetite disturbance
• sleep disturbance
• low energy
• low self-esteem
• poor concentration or difficulty making decisions
• feelings of hopelessness.

The episode must be accompanied by significant clinical distress or impairment in social, occupational, or other key areas of functioning.

Hierarchy rules have been applied to Dysthymia. For the 'with hierarchy' version, a diagnosis can only be made if the initial two-year period of symptoms is free of Major Depressive Episodes and the person has never had a Hypomanic or Manic episode.

An episode is characterised by an abnormally elevated, expansive, or irritable mood lasting at least four days. Three or more of the following symptoms (four if the mood is only irritable) are present:

• inflated self-esteem or grandiosity
• decreased need for sleep
• increased talkativeness
• flight of ideas or the feeling that thoughts are racing
• distractibility
• increase in goal-directed activity or psychomotor agitation
• excessive involvement in pleasurable activities that have a high potential for painful consequences.

While the episode is associated with an unequivocal change in functioning, that is uncharacteristic of the person when not symptomatic, it is not severe enough to cause marked impairment in occupational functioning or in usual social activities or relationships with others, or to necessitate hospitalisation. There are no psychotic features.

An episode is characterised by an abnormally elevated, expansive, or irritable mood lasting at least seven days (or any duration if hospitalisation is required). Three or more of the following symptoms (four if the mood is only irritable) are present:

• inflated self-esteem or grandiosity
• decreased need for sleep
• increased talkativeness
• flight of ideas or the feeling that thoughts are racing
• distractibility
• increase in goal-directed activity or psychomotor agitation
• excessive involvement in pleasurable activities that have a high potential for painful consequences.

The episode causes marked impairment in occupational functioning, usual social activities, or relationships with others.

The episode may also necessitate hospitalisation to prevent harm to self or others. Psychotic features may be present.

Bipolar I and Bipolar II Disorders are mutually exclusive.

This disorder is characterised by the occurrence of one or more Manic Episodes. Often the person has also had one or more Major Depressive Episodes.

This disorder is characterised by the presence of either:

• Mania (excited episodes) and Major Depressive Episode
• Hypomania (with episodes lasting 14 days or longer) and Major Depressive Episode with the person never having had a Manic Episode.

A maladaptive pattern of alcohol use leading to clinically significant impairment or distress. It is evident that alcohol is responsible for or substantially contributes to physical or psychological harm, or dysfunctional behaviour. A diagnosis was achieved if one or more of the following problems occurred in the same 12-month period:

• failure to fulfil key role obligations at school, work or at home
• recurrent alcohol use in situations which are physically hazardous
• recurrent alcohol-related legal problems
• continued alcohol use despite social and interpersonal problems caused or exacerbated by the effects of alcohol.

Hierarchy rules have been applied to Alcohol Abuse. To meet criteria for the 'with hierarchy' version, a person cannot have met criteria for Alcohol Dependence.

A maladaptive pattern of behaviour in which the use of alcohol takes on a much higher priority for the person that other behaviours that once had greater value. The central characteristic is the strong, sometimes overpowering, desire to consume alcohol despite significant alcohol-related problems. A diagnosis was achieved if three or more of the following problems occurred in the same 12-month period:

• tolerance, e.g., a need for markedly increased amounts of alcohol to achieve intoxication or desired effect
• withdrawal, e.g., characteristic withdrawal syndrome is manifested for alcohol
• using more alcohol or for longer periods than intended
• desire or unsuccessful efforts to cut down or control alcohol use
• a great deal of time obtaining, using, or recovering from the effects of alcohol
• reduction in important activities because of alcohol use
• continued use despite knowing it is causing significant physical or psychological problems that were likely caused or exacerbated by alcohol.

The survey collected information on:

• Abuse-opioids
• Abuse-cannabinoids
• Abuse-sedatives
• Abuse-stimulants.

Substance Abuse is a maladaptive pattern of drug use leading to clinically significant impairment or distress. It is evident that the use of opioids/cannabinoids/sedatives/stimulants were responsible for or substantially contributed to physical or psychological harm, or dysfunctional behaviour. A diagnosis was achieved if one or more of the following problems occurred in the same 12-month period:

• failure to fulfil key role obligations at school, work or at home
• recurrent drug use in situations which are physically hazardous
• recurrent drug-related legal problems
• continued drug use despite social and interpersonal problems caused or exacerbated by the effects of the drug.

Hierarchy rules have been applied to Substance Abuse. To meet criteria for the 'with hierarchy' version, a person cannot have met a diagnosis of Dependence on the same type of substance during the same time period.

The study collected information on:

• Dependence - opioids
• Dependence - cannabinoids
• Dependence - sedatives
• Dependence - stimulants.

Substance Dependence is a maladaptive pattern of drug use in which the use of drugs takes on a much higher priority for the person than other behaviours that once had greater value. The central characteristic is the strong, sometimes overpowering, desire to take the substance despite significant substance-related problems. A diagnosis was achieved if three or more of the following occurred for the same substance in the same 12-month period:

• tolerance, e.g., a need for markedly increased amounts of the drug to achieve intoxication or desired effect
• withdrawal, e.g., characteristic withdrawal syndrome is manifested for the drug
• using more of the drug or for longer periods than intended
• desire or unsuccessful efforts to cut down or control drug use
• a great deal of time obtaining, using, or recovering from the effects of the drug
• reduction in important activities because of drug use
• continued use despite knowing it is causing significant physical or psychological problems that were likely caused or exacerbated by the drug.

A person was considered to have a severe level of impairment if any one of the following occurred in the 12 months prior to interview:

• a diagnosis of Bipolar I Disorder
• Substance Dependence with serious role impairment (two effects experienced 'a lot')
• a suicide attempt and any mental disorder
• at least two areas of severe role impairment in the Sheehan Disability Scale domains because of a mental disorder
• overall functional impairment at a level found in the National Comorbidity Survey Replication (NCS-R) to be consistent with a Global Assessment of Functioning (GAF) Score of 50 or less, in conjunction with a mental disorder.

More information on the calculation of functional impairment and the Global Assessment of Functioning (GAF) Score is provided below.

The following criteria were also considered:

• WMH-CIDI 3.0 version - a person must have also experienced substance dependence with physiological dependence
• New Zealand version - a person must have also experienced substance dependence with serious role impairment (two effects experienced 'a lot')
• Australian version - a person did not require a separate specification of impairment due to substance use. Additionally, their scores on the Sheehan Disability Scale for Substance Use disorders were added to the scores from other modules.

A person was considered to have a moderate level of impairment if they had a 12-month mental disorder and they were not classified as severe, reported at least moderate interference in any Sheehan Disability Scale domains, or had Substance Dependence without substantial impairment.

The following criteria were also considered:

• WMH-CIDI 3.0 version - a person must have also experienced substance dependence without physiological dependence
• New Zealand version - a person must have also experienced substance dependence without serious role impairment.

A person was considered to have a mild level of impairment if they had a 12-month mental disorder, and they were not classified as severe or moderate.

The maximum number of days out of role was derived from responses to various questions within the diagnostic modules (e.g., Depressive Episode, Agoraphobia, Mania, etc). The calculation did not include any days out of role for Substance Use disorders, except for the Australian version.

The maximum number of days out of role was then categorised as follows:

• 1-6 days
• 7-50 days
• 51-365 days

People who had 'no interference' on the Sheehan Disability Scale were assigned '0' days. Where there was a 'not known' or 'not stated' value for the days out of role, a median number of days out of role was assigned.

The Sheehan Disability Scale was used to assess the level of interference in four life domains during the worst period of symptoms in the 12 months prior to interview. The four domains are:

• home management (e.g., cleaning, shopping, care of the house, etc.)
• ability to work
• ability to form and maintain close relationships with other people
• social life.

The Sheehan Disability Scale ranges from '0 to 10', with each number being attributed a notional level of interference:

People were asked to select the number that best described the level of interference their symptoms had on each of the domains. From responses in each of the diagnostic modules, a score was calculated for each domain, representing mild, moderate, or severe interference. The calculation did not include any days out of role for Substance Use disorders, except for the Australian version. The scores were as follows:

An overall level of impairment (mild, moderate, or severe) was derived using each of the domain scores. Where a person had 3 or 4 domains rated as severe, they received an overall assessment of 'severe'; where they had 2 to 4 domains rated as mild, they received an overall assessment of 'mild', otherwise they received an overall assessment of 'moderate'.

The predicted Global Assessment of Functioning (GAF) Score is based on the following:

GAF Score of 50 or less

Maximum number of days out of role = 7-50 days or 51-365 days; and

Sheehan Disability Scale domain score = severe

GAF Score of 51 or more

Maximum number of days out of role = 1-6 days; and

Sheehan Disability Scale domain score = mild.

Within the service utilisation module people were asked about consultations with health professionals including:

• general practitioners (GP)
• psychiatrists
• psychologists
• mental health nurses
• other mental health professionals (including social workers, counsellors, or occupational therapists)
• specialist doctors or surgeons (including cardiologists, gynaecologists, or urologists)
• other health professionals (including dieticians, physiotherapists, or pharmacists).

For each type of health professional endorsed they were asked further questions about consultations for their mental health including the number of consultations, how long consultations lasted, how they were paid for, out of pocket expenses, mode of consultation, and whether they were still seeing the health professional for mental health problems.

For the 12 months prior to interview, people were asked about hospital admissions relating to their mental health problems. Mental health problems included, but were not restricted to, things such as stress, anxiety, depression, or dependence on alcohol or drugs. They were asked to provide the number of overnight admissions, the total number of nights admitted, and whether they were a public or private patient.

People who used services for mental health problems (i.e., consulted a health professional or were admitted to hospital overnight) in the 12 months prior to interview were asked to identify the help they received from a list of five types of assistance:

• information (about mental illness, its treatment, and available services)
• medication
• counselling (psychotherapy, cognitive behaviour therapy or counselling)
• social intervention (help to sort out housing or money problems or to meet people for support or company)
• skills training (help to improve their ability to work, to use their time, to look after themselves or their home).

For each type of assistance, they were asked if they received as much help as they needed and if not, the main reason this was not received.

People who did not use services for mental health problems, but who had symptoms that indicated a potential mental disorder (e.g., feeling sad or uninterested, excitable or irritable, worried or anxious, problems with alcohol use or drugs, etc) were asked whether they felt they needed any help from the list of five types of assistance. For each type of assistance identified, people were asked to select the main reason they did not seek help from a list of categories.

Responses to the perceived need for help questions were classified as:

• no need - people who were not receiving help and felt that they had no need for it
• need fully met - people who were receiving help and felt that it was adequate
• need partially met - people who were receiving help, but not as much as they felt they needed
• need not met - people who were not receiving help but felt that they needed it.

Apart from the consultations with health professionals outlined previously, people were asked about other types of services that they used for their mental health problems in the 12 months prior to the survey interview over the phone or the internet or using other digital technology. Information was collected about the use of:

• Crisis support or counselling services (e.g., Lifeline)
• Treatment programs, training, assessments, or other tools to improve mental health (e.g., MindSpot, MoodGym, MyCompass)
• Mental health support groups, forums, or chat rooms (e.g., SANE, Beyond Blue, or CanTeen forums)
• Information about mental illness, treatment options or services

For each type of help used (excluding information about mental illness, treatment options or services), people were asked how many times they used it, whether a health professional was involved, and the mode of access.

In 2007, people were also asked to indicate whether they consulted a ‘Complementary/ alternative therapist such as a herbalist or naturopath’. In 2020-21 this category was not collected separately, however people may have included these in the ‘Other mental health professional’ or ‘Other health professional’ categories.

The category ‘Other mental health professional’ was labelled ‘Other professional providing specialist mental health services’ in 2007. The category ‘Other health professional’ was labelled ‘Other professional providing general services’. In 2007 both categories used the same examples of health professionals, i.e., ‘social worker, counsellor, occupational therapist’. In 2021, the examples provided for ‘Other health professional’ were ‘dietician, physiotherapist, pharmacist (advice only).

The Kessler Psychological Distress Scale (K10) is a widely used indicator, which gives a simple measure of psychological distress. It is not a diagnostic tool but is an indicator of psychological distress.

The K10 is based on a person's emotional state during the 4 weeks prior to the survey interview. People were asked a series of 10 questions, about how often they felt:

1. tired for no good reason
2. nervous
3. so nervous nothing could calm them down
4. hopeless
5. restless or fidgety
6. so restless that they could not sit still
7. depressed
8. that everything was an effort
9. so sad that nothing could cheer them up; and
10. worthless.

For each question, an answer was provided using a five-level response scale, based on the amount of time a person reported experiencing the problem. The response scale corresponded to the following:

• none of the time
• a little of the time
• some of the time
• most of the time
• all of the time.

If a person selected 'none of the time' for questions 2 or 5 they were not asked the follow-on questions at 3 or 6 but were skipped to subsequent questions at 4 or 7 respectively.

Scores for the 10 questions were put together, with a minimum possible score of 10 and a maximum possible score of 50. Low scores indicate low levels of psychological distress, and high scores indicate high levels of psychological distress. The scores output were:

Four ‘plus’ questions are used to assess functioning and how often the feelings were caused by physical health problems.

Comparability with 2007

There were slight changes to the question wording, with the 2020-21 study referring to the 4 weeks prior to interview, compared to the 30 days prior to interview in 2007.

In 2007, questions 8 and 9 of the K10 were asked in the reverse order and the endorsement of 'none of the time' for question 7 resulted in a person being skipped to question 9. Additionally, the 2007 questions asked how often the person felt so ‘depressed’ rather than so ‘sad’ that nothing could cheer them up.

A selected group of questions from the Living in the Community Questionnaire - Summary (LCQ-S) were included in the study for the first time in 2020-21. The LCQ-S was developed by the Australian Mental Health Outcomes and Classification Network (AMHOCN) to assess social support and societal participation of Australians. 

The WHO Disability Assessment Schedule (WHODAS) 2.0 is a simple tool used to assess health and disability. It directly relates to the concepts in the International Classification of Functioning, Disability and Health (ICF). It covers six domains of functioning including:

• Cognition – understanding and communicating
• Mobility– moving and getting around
• Self-care– hygiene, dressing, eating & staying alone
• Getting along– interacting with other people
• Life activities– domestic responsibilities, leisure, work, and school
• Participation– joining in community activities.

For each question, an answer was provided using a five-level response scale, based on the amount of difficulty a person experienced in undertaking the activity, on average, over the last 30 days due to their health conditions. The response scale corresponded to the following:

• None
• Mild
• Moderate
• Severe
• Extreme/Cannot do

The 12-item version of the questionnaire was used for the 2020-21 study.