In order to diagnose a depressive disorder the health professional or family doctor would do a full evaluation including questions regarding family history, personal history of illness and recent stressors.

Other family members and friends may be interviewed in order to obtain further information and to assess the level of support.

A physical examination may be carried out or requested in order to exclude underlying physical illnesses, which could cause or contribute to a depressive disorder. Special investigations such as blood tests or sometimes even a brain scan may be requested if an underlying organic problem is suspected.

Specific diagnostic criteria have been set down in the DSM-IV (Diagnostic and Statistical Manual of Mental Disorders, 4th edition) to diagnose a Major Depressive Episode. These are described below:

The presence of five of the following nine symptoms occurring for most of the time during the same two week period resulting in a change in the level of functioning. The symptoms cause significant distress or obvious changes in social and occupational functioning.

One of the first two symptoms following must be present in order to make the diagnosis:

 
• a depressed mood (may be irritability in children);  
• loss of interest or pleasure in previously enjoyed activities;  
• appetite changes with significant weight loss (when not dieting) or weight gain;  
• increased sleep or insomnia;  
• slowing or speeding up of physical activity;  
• fatigue or loss of energy;  
• feeling of worthlessness or excessive or inappropriate guilt;  
• decreased ability to think or concentrate or indecisiveness;  
• recurrent thoughts of death or recurrent suicidal ideation.