The 2020-21 NSMHW was designed to be broadly comparable with the 2007 survey. It used the WMH-CIDI 3.0 questionnaire modules used in 2007 and collected them in the same order as they were collected in 2007. Data collected using the WMH-CIDI 3.0 modules are therefore comparable between 2020-21 and 2007.
Many of the non-diagnostic topics and the order in which they were collected in the 2020-21 survey differs from that in 2007. Some topics collected in the 2007 survey were removed and new topics were added. Other topics changed significantly between 2020-21 and 2007. For example, demographic and socio-economic modules were updated to align with current ABS standards and commonly used ABS questions and data items. Data for non-diagnostic topics may not be comparable between 2020-21 and 2007.
Please see the Data Item Lists for each collection for full details.
Due to the change in questions used to collect physical health conditions in the 2020-21 survey, the comorbidity of mental health disorders and physical health conditions is not comparable with 2007.
The diagnoses of mental disorders are based on the WMH-CIDI 3.0 algorithms. The algorithms operationalise criteria from two classification systems: the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (DSM-IV); and the WHO International Classification of Diseases, Tenth Revision (ICD-10).
The version of the algorithms used for the 2020-21 survey was provided by the WHO in 2020. The algorithms are comparable with the version used for the 2007 survey with the following exceptions:
ICD-10 Post-Traumatic Stress Disorder (PTSD):
- ICD criteria B Part 2 has been updated: Group 2 reactions (unwanted memories, unpleasant dreams, flashbacks, getting very upset when reminded of it, physical reactions) must have occurred at least once a month. The version of the diagnostic algorithms used for the 2007 survey did not include the once-a-month persistence criterion.
- ICD criteria D Part 2 has been updated: Persistent symptoms of increased psychological sensitivity and arousal shown by any two of the following: difficulty in falling or staying asleep, irritability or outbursts of anger, difficulty in concentrating, hypervigilance, exaggerated startle response; not present before exposure to the stressor, and must have occurred at least once a month. The version of the diagnostic algorithms used for the 2007 survey did not include the once-a-month persistence criterion.
- Lifetime and 12-month prevalence data items for ICD-10 PTSD are therefore not comparable between 2020-21 and 2007.
ICD-10 Obsessive-Compulsive Disorder (OCD):
- For an ICD-10 lifetime diagnosis of OCD, obsessions and/or compulsions must be present on most days for at least two weeks. In 2007, the 12-month diagnosis was derived from the lifetime diagnosis including the criterion that disorder symptoms must have been present on most days for at least two weeks or longer in the 12 months prior to the survey interview. The version of the algorithms used for the 2020-21 survey did not include the two-week persistence as a condition for meeting 12-month diagnosis. 12-month diagnosis in 2020-2021 is derived based on lifetime OCD diagnosis with the presence of OCD symptoms, for any duration, in the past 12 months.
- 12-month prevalence data items for ICD-10 OCD are therefore not comparable between 2020-21 and 2007.
Both Post-Traumatic Stress Disorder and Obsessive-Compulsive Disorder are classified as Anxiety disorders. Consequently, the ICD-10 lifetime and 12-month Anxiety disorders data items and the ICD-10 lifetime and 12-month Mental disorders data items are also not comparable between 2020-21 and 2007.