How is a diagnosis of mental illness reached?

Mental illness cannot be diagnosed by a physical test. Reaching a diagnosis is not a simple process.

People refered to mental health services often do not have a definitive diagnosis.

For a psychiatrist to diagnose a mental illness

• the person must be showing that his or her thought patterns, perceptions, emotions and behaviour have changed (e.g. symptoms of hallucinations, delusions or apathy)
• it must be clear that the symptoms and behaviour have followed a recognisable pattern over a period of time (e.g. a decreased ability to work, to relate to others or to take care of him or herself as a result of the illness).
• continuous signs of the illness must have been present for at least six months

The ICD 10 is the international standard diagnostic classification for all physical and mental disorders, chapter 5 covers 'mental and behavioural disorders' and can be downloaded from the WHO website.