Depression

major depressive disorder (mdd) criteria

• five or more of the following symptoms have been present during the same 2-week period; at least one of the symptoms is either depressed mood (1) or loss of interest or pleasure (2)

  • depressed mood most of the day, nearly every day

  • markedly diminished interest or pleasure in all, or almost all activities most of the day, nearly every day

  • significant weight or appetite change

  • insomnia or hypersomnia nearly every day

  • psychomotor retardation or agitation nearly every day

  • fatigue or loss of energy nearly every day

  • feelings of worthlessness or excessive guilt nearly every day

  • diminished ability to think or concentrate nearly every day

  • recurrent suicidal ideation, plan, or attempt

    • significant distress or impairment

    • symptoms not due to substance use or medical problem

    • symptoms not better explained by another disorder

    • there has never been a manic or hypomanic episode

• NOTE: responses to a significant loss (e.g., bereavement, financial ruin, losses from a natural disaster, a serious medical illness or disability) may include the feelings of intense sadness, rumination about the loss, insomnia, poor appetite, and weight loss noted in Criterion A, which may resemble a depressive episode

• although such symptoms may be understandable or considered appropriate to the loss, the presence of a major depressive episode in addition to the normal response to a significant loss should also be carefully considered

• this decision inevitably required the exercise of clinical judgment based on the individual’s history and the cultural norms for the expression of distress in the context of loss

impact of depression

• disability-adjusted life years (DALYs)

  • metric for describing impact/impairment of diseases, disorders, injuries, and conditions

  • DALY: years of life lost + years lived with disability (lost years of healthy life)

  • 13.6% of DALYs are caused by mental/behavioral disorders

  • major depression carries the heaviest burden (3.73% of DALYs)

epidemiology

• epidemiology: study of distribution, patterns, and determinants of health and disease in populations

• lifetime prevalence of MDD

  • % who meet criteria at some point in lifetime

  • 16.6% (Kessler et al., 2012)

• current prevalence of MDD

  • % currently meeting criteria

  • 7.1% (Kessler et al., 2012)

course and outcome

• age at onset

  • average = 24 to 29 years old

  • earlier onset worsens prognosis

  • rates increase during adolescence

  • sex difference in rate first appears in early adolescence, with females being at higher risk than males

• number of major depressive episodes

  • lifetime average = 4

  • average length = 4.5 months

  • ~25% of people have 6+

etiology of MDD

• etiology: the cause, set of causes, or manner of causation of a disease or condition

• biopsychosocial model

  • suggests biological, psychological, and social factors all influence the development of MDD

  • framework for organizing potential etiological influence on psychopathology

• biological influences

  • genes- abnormal genes (typically in interaction with environment)

  • neurotransmitter systems- dysregulation of neurotransmitters and receptors

  • neurophysiology- abnormalities in structure and functioning of brain regions

  • neuroendocrine system- altered activity in the hypothalamic-pituitary-adrenal (HPA) axis

• genetic influences

  • behavior genetics- study of the degree to which genes and environment influence behavior

    • doesn’t tell us which genes are responsible

    • helps establish heritability of mental illnesses

      • percentage of variation in characteristic that us attributable to genetic influences

      • depression: 37% -50% (Sullivan et al., 2012)

  • molecular genetics- study of influence of specific genes and environment on behavior

    • MDD is polygenic

      • associated with configuration of several irregular genes, not with single disordered gene

  • challenges facing molecular genetics- attempts to find specific genes involved in MDD (and other clinical phenomena) plagued by large number of non-replications

    • genetic influences on mental illness polygenic- associated with configuration of several irregular genes, not with single disordered gene

    • genes unlikely to lead directly to clinical problems- produce brain, neurochemical, hormonal changes that lead to clinical problems/ interact with environments events to lead to clinical problems

  • genetic influence are not fixed but unfold and change across development in dynamic interaction with environmental factors

• neurotransmitter influences

  • neurotransmitters: chemicals that facilitate communication across synapses between neurons

    • released into synaptic gap to bind with receptors on post-synaptic membrane

  • abnormalities in the number and sensitivity of receptors for monoamine neurotransmitters may be implicated in MDD