Neuroscience/Objectives/Lecture 7

From PhysioWiki

Clinical correlate: depression

DESCRIBE the different types of mood disorder.

There are four broad types of mood disorders, including bipolar disorder, adjustment disorder with depressed mood, mood disorders due to general medical condition and substances, and depressive disorders. The latter includes unspecified depressive disorders, dysthymic disorders, and single-episode or recurrent major depression, with or without psychosis.

A major depressive disorder is characterized by:

1. Two-week(+) period of maladaptive functioning that is a clear change from previous functioning
2. At least five of the following symptoms (must include the first or second bullet):
   • depressed mood
   • anhedonia
   • appetide disturbance with >5% weight change within a month
   • sleep disturbance
   • psychomotor changes
   • fatigue
   • worthlessness, inappropriate guilt
   • attention, concentration, decision-making problems
   • suicidality
3. Marked distress and/or significant social and occupational impairment
4. No evidence of physical or substance-induced etiology or presence of other disorder that would account for patient's depressive symptoms

Dysthymia is characterized by:

1. Depressed mood most of the day for at least two years (one year in children)
2. At least two of the following symptoms while depressed:
   • Appetite changes (poor appetite, overeating)
   • Sleep changes (insomnia or hypersomnia)
   • Fatigue
   • Low self-esteem
   • Concentration, decision-making problems
   • Hoplessness
3. Never been without symptoms for more than two months at a time
4. Disturbance not better accounted for by major depressive disorder or major depressive disorder in partial remission
5. Never been a manic episode, mixed episode, or hypomanic episode; cyclothymic disorder criteria never met
6. Does not occur exclusively during chronic psychotic disorder (e.g. schizophrenia or delusional disorder)
7. Not due to substance or medical condition
8. Symptoms cause clinically significant distress or social impairment

Depressive disorders not otherwise specified include all other depressive disorders not accountded for by major depression, dysthymia, adjustment disorder or a general medical condition. Can be present as part of an anxiety disorder.

DESCRIBE the diagnostic criteria for major depression.

See above.

REVIEW the different theories of depression.

• Biological factors
  • Biogenic amines: imbalance between NE, 5-HT, and DA
    • Reserpine depletes monoamines and causes depression
    • MAOIs prevent NE and 5-HT destruction and alleviate depression
    • CSF 5-HIAA (a 5-HT metabolite) low in suicidal individuals
    • Low dietary tryptophan leads to depression
    • Most antidepressants elevate monoamines in the CNS
  • Structural plasticity
    • Stress -> atrophy -> hippocampal death -> depression
    • Lithium increases hippocampal neurogenesis -> alleviation of depression
  • Neuroendocrine regulation
    • Dysfunctional neurotransmitter regulation
  • Neuroimmune regulation
    • Cytokine treatment -> depression
    • Terminate cytokine treatment -> alleviation
  • Neuroanatomical considerations
    • Decreased gray matter in prefrontal cortex, ventral striatum, hippocampus
    • Neurological disorders of basal ganglia and limbic system
  • Kindling theory
    • Exposure to depressive events (kindling) lowers threshold at which mood changes occur
    • Some are genetically predisposed to enhanced lowering of this threshold
    • Periods of depression typically recur and may become more frequent as a consequence
• Genetic factors
  • Family studies: family relatives 2-3 times more likely to be depressed if family member is depressed
  • Adoption studies: biological, environmental effects
  • Twin studies: 50% concordance in monozygotic twins; 10-25% in dizygotic twins
  • Linkage studies: no consistent genetic linkage
  • Intermediate phenotypes: future; trying to find specific reuptake systems
• Psychosocial factors
  • Life events: stressful events often precede first and subsequent episodes of mood disorders
  • Premorbid personality factors: dependent, obsessive-compulsive, histrionic
  • Psychodynamic factors
    • Depressed rage internally directed because of identification with lost object
    • Partial or complete collapse of self-esteem within the ego
  • Learned helplessness: patient learns they're helpless in face of adversity
  • Cognitive theory: leaerned negative views of self

UNDERSTAND the natural course of the illness.

Major depression usually develops over days to weeks. Dysthymia may develop over months and is more chronic. A prodromal period may include anxiety symptoms and mild depression that may last weeks or months before actual major depression onset. Left untreated, an episode may last six months or more.

Most (60-70%) of cases end in complete remission with function returning to premorbid levels. In remaining cases, symptoms insufficient to meet criteria for major depression persist for months to years (partial remission), and may be associated with disability or distress.

Risk of developing second depressive episode is 50%. Risk of developing a third is 70%. Thus, after a third episode, continuous antidepressive treatment is usually recommended because of the likely event of recurrence.

DESCRIBE the different therapeutic approaches for the treatment of depression.

• Pharmacotherapy (e.g. SSRI, lithium, Wellbutrin)
  • About 60% of subjects have moderate to full response
  • 30-40% may need other antidepressant
  • Response may be augmented with secondary antidepressant
• Psychotherapy
  • Supportive therapy
  • Cognitive behavioral therapy
  • Interpersonal therapy
  • Psychoanalytically oriented therapy
  • Family therapy