Department of Health

Key messages

  • Depression is a serious illness that affects a person’s behaviour, thoughts, feelings and physical health.
  • Depression can occur at any age.
  • Depression is characterised by a variety of symptoms and can be acute or chronic and range from mild to severe.

Depression is more than a low mood; it is a serious illness that impairs a person’s ability to function and causes significant distress for them and their family1.

Depression presents as a complex combination of:

  • behaviours – such as withdrawing from people and activities, neglecting personal appearance and commitments
  • thoughts for example, indecisive, negative comments
  • feelings– such as moodiness and irritability
  • physical symptoms – for example, unexplained headaches or pain, digestive upsets or nausea, dizziness, constipation.

Depression can be an acute or chronic condition. It can occur for the first time in an older person (referred to as late onset or late-life depression) or can be a recurrence or relapse of a previous episode2.

Characteristics of clinical depression

Clinical depression (major depressive disorder or depressive episode) is characterised by five or more of the following symptoms during the same two-week period. The symptoms must represent a change in functioning and include a depressed mood or loss of interest or pleasure. Symptoms include the following3:

  • Depressed mood most of the day, nearly every day (subjectively reported or objectively observed; for example, reports feeling sad or empty; appears tearful).
  • Marked decreased interest or pleasure in all, or almost all, activities most of the day, nearly every day (subjectively reported or objectively observed).
  • Significant weight loss or gain (more that five per cent of body weight in a month) or increased or decreased appetite (nearly every day).
  • Insomnia or hypersomnia (feeling sleepy throughout the day) nearly every day.
  • Psychomotor agitation or retardation nearly every day (observable and not merely subjective feelings of restlessness or being slowed down). For example, unintentional and purposeless movements due to mental tension (such as pacing or hand wringing); or slowing of thought, coordination and speech, presenting as sluggishness or confusion in speech.
  • Fatigue or loss of energy nearly every day.
  • Feelings of worthlessness or excessive or inappropriate guilt (may be delusional) nearly every day (not merely self-reproach or guilt about being sick).
  • Diminished ability to think or concentrate, or indecisiveness, nearly every day (subjectively reported or objectively observed).
  • Recurrent thoughts of death (not just fear of dying) or suicidal ideation without a specific plan, or a suicide attempt or specific plan for committing suicide.
  • These symptoms cannot be attributed to direct physiological effects of a substance or general medical condition.

Subtypes of major depression include melancholic (a severe form of depression where many of the physical symptoms are present, particularly moving slowly, and where more likely there is a loss of pleasure in most or all things), non-melancholic and psychotic (include hallucinations and delusions)1.

Severity of depression

Depression can be divided into four categories of severity:

  • Mild: characterised by five to six symptoms with mild functional impairment or the capacity to function normally with substantial effort.
  • Moderate: lies between mild and severe.
  • Severe (without psychotic features): characterised by the presence of most of the symptoms with observable functional impairment.
  • Severe with psychotic features: also includes delusions (for example, false beliefs, typically of being a bad person, deserving punishment or that bad things will happen) and hallucinations (such as hearing voices, smelling bad smells or other physical sensations).

1. Jorm, A.F., et al., A guide to what works for depression, 2013, Beyond Blue: Melbourne.

2. National Ageing Research Institute, Depression in older age: A scoping study, 2009, National Ageing Research Institute: Parkville.

3. Diagnostic and Statistical Manual of Mental Disorders, 5th edition.

Reviewed 05 October 2015


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