Depressive Disorders (College Board AP® Psychology): Study Guide

Symptoms of major depressive disorder (MDD)

• Depressive disorders involve persistent low or irritable mood, alongside cognitive and physical changes that impair functioning

  • They are more than normal sadness, as they are prolonged, pervasive, and disabling

• Two disorders include:

  • Major Depressive Disorder (MDD)

  • Persistent Depressive Disorder (PDD)

• MDD is the most common psychological disorder

  • It involves one or more major depressive episodes lasting at least two weeks

• Core symptoms include (at least one required):

  • Depressed mood most of the day, nearly every day

    • The person has persistent sadness, emptiness, or hopelessness

  • Loss of interest or pleasure in almost all activities (anhedonia)

    • Activities that were previously enjoyable no longer produce pleasure

• Additional symptoms include:

  • Significant weight gain or loss, or changes in appetite

  • Insomnia or hypersomnia

    • sleeping too little or too much

  • Psychomotor agitation

    • restlessness (inability to sit still) or retardation (slowed movement, speech)

  • Fatigue or loss of energy nearly every day

  • Feelings of worthlessness or excessive guilt

  • Difficulty concentrating, or making decisions

  • Recurrent thoughts of death or suicidal ideation

• Symptoms must cause significant distress or impairment in social, occupational, or other important areas of functioning

• MDD can range from mild to severe

  • In severe cases it may include psychotic features (e.g. depressive delusions)

Persistent depressive disorder (PDD)

• Persistent depressive disorder (formerly known as dysthymia) is a chronic form of depression

  • Symptoms are similar to MDD but are typically less intense

  • Symptoms persist for most of the day, more days than not, for at least two years

  • Periods of normal mood last no more than two months during the two-year period

• PDD is often described as a low-grade but long-term depression

  • E.g. someone who has felt persistently low and unmotivated for years but continues to function at a reduced level

Causes of depressive disorders

• Depression is best understood as the result of interacting biological, psychological, and social factors

Biological causes

• Genetic factors: depression is heritable

  • First-degree relatives of people with MDD have elevated rates of the disorder

  • Twin studies show higher concordance in identical than fraternal twins

• Neurochemical factors: low levels of serotonin and norepinephrine are linked to depression

  • This is supported by the effectiveness of antidepressant medications (SSRIs, SNRIs) that increase the availability of these neurotransmitters

  • However, depression is not explained by a simple “chemical imbalance”

• Brain structure: depression is associated with reduced activity in the prefrontal cortex and dysregulation of the limbic system

Psychological causes

• Cognitive causes: depression arises from the cognitive triad of negative thoughts about:

  • the self — "I am worthless and inadequate"

  • the world — "Everything I experience is a failure and a burden"

  • the future — "Nothing will ever improve"

  • These negative thought patterns are maintained by cognitive distortions and pessimistic thinking

• Behavioral causes: depression is maintained when avoidance behavior is negatively reinforced

  • Withdrawing from activities reduces the opportunity for positive reinforcement, deepening the depressive cycle

• Learned helplessness: repeated experience of uncontrollable negative events leads to a generalized expectation that effort is futile

Social and cultural causes

• Social factors: lack of social support, social isolation, and absence of meaningful relationships are significant risk factors for depression

• Cultural factors: rates of depression vary across cultures

  • Depression is more prevalent in the United States than in many other countries

  • Cultural norms shape how depression is expressed and whether it is recognized and treated

• Adverse life events: bereavement, relationship breakdown, job loss, and trauma are significant precipitating factors

  • This is consistent with the diathesis-stress model