When assessing and diagnosing abnormality, various assessment tools can be used in order to determine a possible diagnosis of a mental illness. Various methods of assessment include clinical interviews, cognitive, symptom, and personality tests, and behavioural observation and self-monitoring. These tests involve extensive prior research to ensure their reliability and validity in terms of measuring what they're supposed to measure and consistently giving the appropriate results.
In clinical interviews, the clinician obtains initial information about the client. This can include basic information about the client's life, including their family history, social environment, major events, and daily life. More specific questions can explore the individual's symptoms, including frequency and magnitude.
More specific assessments can be made to determine specific functioning of the individual. For instance, cognitive tests, intelligence tests, personality tests, and neuropsychological tests may be used. Brain-imaging techniques and questionnaires to determine symptoms and history can also be utilized to collect information for in assessing and diagnosing abnormality.
Lastly, individuals can be assessed based on their behaviour, which can be done via monitoring the client and their interactions within the environment. The individual can also report back to the clinician through self-monitoring their own behaviour and thoughts in methods such as journaling.
Using this information, combined with specific assessment tools and clinical interviews, the client can be appropriately assessed in terms of their symptoms, history, functioning, and behaviour in order to get an overall idea of their mental health.