In order for a diagnosis of depression to be reached, the patient must have, for most days over the past month, at least one of the following core symptoms:

• Feeling down, depressed or hopeless
• Little pleasure or interest in doing things.

There must also be four of the following present:

• Fatigue or low energy levels
• Feeling worthless or inappropriately or excessively guilty
• Recurrent thoughts of death, or an attempt at suicide
• Reduced ability to think, concentrate or make decisions
• Psychomotor agitation or retardation
• Insomnia or hypersomnia
• Significant appetite and/or weight loss.

Atypical symptoms of note include reactive mood, increased appetite, weight gain, excessive sleepiness and sensitivity to rejection.

Red flag signs and symptoms

The following indicate that an urgent referral to specialist mental health services is warranted:

• Active suicidal ideation or planning
• Symptoms of psychosis
• Severe agitation alongside severe symptoms of depression
• High levels of self-neglect
• Posing an immediate risk to others.