Severe clinical depression is usually quite easy for a medical practitioner, psychiatrist or clinical psychologist to recognize. However, only around 20% of clinical depression cases are diagnosed. This is mainly because it can "mask" itself as a physical illness such as chronic pain or fatigue.

Symptoms that can indicate clinical depression include a depressed mood, loss of interest or enjoyment, low energy level and fatigue and tiredness only after slight effort. These are the most common signs, but someone with clinical depression can also experience a reduction in concentration and attention, low self-esteem and confidence, feelings of guilt and worthlessness, pessimistic views of the future, ideas of self-harm and / or suicide, disturbed sleep, and loss of appetite.