Depression

Types of Depression & Characteristics of Affective Disorders

Affective Disorders:

  • Major contributor to premature death and disability.

  • 1 in 7 UK adults report poor mental health in 2024, up from 1 in 10 pre-pandemic.

  • Disproportionate impact on women (18.5% vs. 12.5% for men).

  • NHS expenditure on mental health: £12 billion, 8% of total budget.

Types:

  • Unipolar Depression: Persistent sadness, often reactive (75% environmental) or endogenous (25% genetic).

  • Bipolar Depression: Mood oscillation between depression and mania, with a hereditary tendency.

Other Types:

  • Cyclothymia: Milder mood fluctuations, considered a mild bipolar form.

  • Major Depressive Disorder: Severe, disabling, not drug or medical-condition induced.

  • Dysthymic Disorder: Chronic, less severe form of major depression.

  • Seasonal Affective Disorder (SAD): Depression recurring seasonally, e.g., in winter.

Diagnosing Depression

  • Challenges: Broad symptom range, lack of objective diagnostic test, relies on patient interview/questionnaire.

  • Diagnostic Tools:

    • DSM-5 (American Psychiatric Association)

    • ICD-10/11 (World Health Organization)

DSM-5 Criteria: Five or more symptoms for at least two weeks, including depressed mood or loss of pleasure.

  • Key Symptoms: Depressed mood, anhedonia, weight change, sleep disturbances, fatigue, feelings of worthlessness, cognitive difficulties, suicidal thoughts.

Who Gets Depression?

  • Gender: Depression is twice as common in females.

  • Age: Usually first appears in late adolescence or early adulthood. Rising diagnosis rates could indicate more stress or increased recognition.

Comorbidity and Suicide Risks

  • Suicide: Common in those with depression; 20% attempt, 10% complete suicide.

  • Comorbid Conditions:

Often coexists with anxiety, substance abuse, chronic illness (e.g., cancer, thyroid issues, neurological disease, coronary heart disease).

Depression with anxiety shows increased severity and suicide risk, lower treatment response.

Causes of Depression

  • Genetic Predisposition: Higher rates in close relatives, especially identical twins.

  • Environmental Factors: Stressful life events, social isolation, bullying.

  • Physiological Factors: Hormonal changes (thyroxine, postpartum, menopause).

Theories of Depression

  1. Monoamine Theory (Schildkraut, 1965):

  • Depression linked to reduced activity of noradrenergic and serotonergic systems.

  • Antidepressants increase monoamine levels but often take weeks for effects, suggesting adaptation rather than immediate chemical effects.

  1. Neuroendocrine Theory:

  • HPA Axis Hyperactivity: Increased cortisol in depressed patients due to excess CRH.

  • Reduced Hippocampal Feedback: Fewer glucocorticoid receptors, linked to early life stress.

  • Early sensory experiences influence glucocorticoid receptor expression, which may affect long-term mood regulation.

  1. Neuroplasticity & Neurogenesis:

  • Depression linked to neuronal loss in the hippocampus and prefrontal cortex.

  • Antidepressants and ECT promote neurogenesis; SSRIs increase glucocorticoid receptors in the hippocampus.

Other Factors: Oxidative stress, neuroinflammation, gut-brain axis imbalances.

Integrated Approach:

  • Depression may involve neurotransmitter imbalances, gene expression changes, and neuroinflammation, rather than a single neurotransmitter deficit.