Chapter 19: Depression

INTRODUCTION

Depressive illness, which is probably the greatest masquerade in general practice, is one of the commonest illnesses in medicine and often confused with other illness. Untreated, depression can result in disability and death.¹ It is present in at least 17% of patients who present to GPs² and has a 12-month prevalence of 5% and a lifetime risk of 15%.³ It is often unrecognised,¹ yet moderate to severe depression is as disabling as congestive heart failure¹ and with a morbidity comparable to coronary heart disease. Further, depression is the leading cause of disability for all conditions among both sexes, both in Australia and worldwide.^4,5 The lifetime risk of suicide in patients diagnosed with depression is 6% and treatment halves this risk.¹

Despite being treatable, 60% of sufferers have not used any form of health service in the previous months.⁴ Lack of awareness, stigma and shame on behalf of the patient contribute to this. Of those receiving treatment, three-quarters will be managed in general practice.^5,6 As Whitford⁴ notes:

Depression is a chronic relapsing organic brain disease. Its mean onset is at 27 years of age. However, 40% of sufferers present by 20 years of age.⁷ The average duration of episodes is 3–4 months and 40% of patients will relapse within a 12-month period.⁷

The cause of depression is multifactorial, having biological, psychological and social factors. Mood disorders in general have a strong familial tendency, and the risk of developing a depressive disorder can be thought of in terms of a ‘stress-vulnerability model’. That is, an individual may have a genetically determined vulnerability and if enough stress is endured a mood disorder may result. Those who are more genetically vulnerable require less stress, but if enough stress is applied, any individual can develop a mood disorder.

There are six clusters of depressive symptoms:

• mood, e.g. sadness, anhedonia, irritability

• vegetative, e.g. sleep, appetite, sexual drive

• cognitive, e.g. attention, memory, self-worth

• impulse control, e.g. suicide, anger, homicide

• behavioural, e.g. motivation, interests, tiredness

• physical, e.g. headaches, constipation

A useful working rule is to consider depression as an illness that dampens the five basic innate activities of humans:

• energy for activity

• sex

• sleep

• appetite and thirst

• elimination of waste

CLASSIFICATIONS

• The DSM-5 classification divides depressive disorders into major depressive disorder (MDD), disruptive mood ...