MAjor Depressive Disorder

Genetics
1. no genes have been linked to depression
  1. CAMP ET AL 2005
2. Pairing together 2 diff syndromes
  1. early on-set depression - high probability of other relatives with depression
    1. BIERUT ET AL 1999
    2. aswell as anxiety disorders, attention-deficit disorder, alcohol abuse
  2. late on-set have high probability of relatives with circulatory problems
3. effect of gene varies with environment
  1. one controls serotonin transporter
    1. Protein regulates ability of axons to reabsorb serotonin after release, to recycle for further use
      1. short and long type (no replications been found)
        short type - increase in stressful experiences led to big increase in depression
        long type - stress events only slightly increased risk of depression
        1 long 1 short - were intermediate
        short form of gene alone didn't lead to depression but might magnify reaction to stressful events
        CASPIT ET AL 2003
4. if a study finds no significant correlation between 2 variables, perhaps 1 or both of variables was poorly measured
  1. measurement of depression are good but problems with measurement of stress
    1. some events will be more stressful for some people than they are for others.
      1. WRAY ET AL 2009
Other Bio Influence
1. viral infections
  1. Borna disease
    1. viral infection of fair animals, produces periods of frantic activity alternating with periods of inactivity
    2. 1985, tested 370 people for exposure
      1. AMSTERDAM ET AL 1985
      2. 12 Bornea and depression
      3. 5% normal people and 1/3 those with depression or schizo
    3. e predisposing factor in some cases
2. Hormones
  1. stress is important & increases cortisol
    1. 20% women report postpartum depression
      1. suspect hormonal fluctuations are contributing factor
      2. stress hormones reach peak late in preg and ovarian hormones change during delivery
        after drug-induced drop in estradiol and progesterone levels, women with history of PPD suddenly show new symptoms of dep
        BLOCK ET AL 2000
    2. declining level of hormone testosterone assoc. with increased prob of sep
  2. few studies have links hormones to dep & rship remains uncertain
Abnormalities of Hemispheric Dominance
1. normal people found strong rship between happy mood and increased activity in left prefrontal cortex
  1. JACOBS & SNYDER 1996
  2. Dep people decreased activity in left and increased activity in right prefrontal cortex
    1. this imbalance is stable over years despite changes in symptoms of depression
2. Most people gaze to the right during verbal tasks but dep gaze left showing right-hemisphere dominance
  1. LENHART & KATKIN 1986
people with major depression feel sad, helpless everyday for weeks at a time
1. feel worthless have little energy
2. absence of happiness is more reliable symptom than increased sadness
3. decreased response to happy facial expressions and decreased response to a likely reward
  1. MONK ET AL 2009
4. standards for diagnosis vary - no lab tests to confirm diagnosis to stats vary
5. depression in childhood is equal for boys and girls
  1. 14+ its more common in females
    1. TWENGE & NOLEN-HOCKSEMA 2002
6. Most people suffer from episodes separated by periods of normal moods.
  1. rat episode is longest and triggered by an event

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MAjor Depressive Disorder

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