Introduction
Depression is a common yet potentially serious mental health condition that affects many Australians and New Zealanders. Although most people feel sad or down from time to time, a depressive illness or clinical depression is characterised by a sustained period of low mood and anhedonia (i.e., loss of pleasure), as well as other cognitive, emotional, and biological markers. The Diagnostic and Statistical Manual of Mental Disorders (5th ed.; DSM-5; American Psychiatric Association, 2013), has now listed only unipolar depressive disorders within its own chapter. This deviates from previous editions (DSM-III through to DSM-IV-TR) where depressive disorders appeared in a mood disorders chapter and were listed in the same chapter as bipolar disorders.
In the DSM-5, two new depressive disorders have been added: disruptive mood dysregulation disorder and pre-menstrual dysphoric disorder. Major depressive disorder (MDD), dysthymia, substance-induced depressive disorder, and depressive disorder due to a medical condition have been retained with some minor variations in some of the diagnostic criteria. Most people diagnosed with a depressive disorder would have MDD. Generally, when clinicians and public health policymakers discuss depressive disorders, they mean MDD. This chapter will mostly focus on MDD (the term “clinical depression” is used interchangeably with MDD in this chapter).
To be diagnosed with MDD, the individual must have five or more of the following features for a 2-week period: the presence of low mood and/or anhedonia (one of these is mandatory); significant weight loss or weight gain; disturbed sleep; psychomotor agitation or slowing; listlessness; feelings of self-deprecation or guilt; poor concentration; and reoccurring thoughts of death and/or suicide (this may include a plan for suicide).
Australian and New Zealand (NZ) governments have recognised the personal, social, and economic ramifications of depression over the last decade. MDD has been directly linked to suicide, as well as family and relationship issues including parenting difficulties, poorer physical health (including diabetes and heart disease), poorer work productivity, greater workers’ compensation claims, and greater sick leave. Organisations in both Australia and NZ have adopted numerous initiatives to increase the public understanding of depression, reduce the stigma associated with depression, and ultimately prevent and treat depression.