MAjor Depressive Disorder

MAjor Depressive Disorder

1. Genetics

   • no genes have been linked to depression
     • CAMP ET AL 2005
   • Pairing together 2 diff syndromes
     • early on-set depression - high probability of other relatives with depression
       • BIERUT ET AL 1999
       • aswell as anxiety disorders, attention-deficit disorder, alcohol abuse
     • late on-set have high probability of relatives with circulatory problems
   • effect of gene varies with environment
     • one controls serotonin transporter
       • Protein regulates ability of axons to reabsorb serotonin after release, to recycle for further use
         • 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
   • if a study finds no significant correlation between 2 variables, perhaps 1 or both of variables was poorly measured
     • measurement of depression are good but problems with measurement of stress
       • some events will be more stressful for some people than they are for others.
         • WRAY ET AL 2009

2. Other Bio Influence

   • viral infections
     • Borna disease
       • viral infection of fair animals, produces periods of frantic activity alternating with periods of inactivity
       • 1985, tested 370 people for exposure
         • AMSTERDAM ET AL 1985
         • 12 Bornea and depression
         • 5% normal people and 1/3 those with depression or schizo
       • e predisposing factor in some cases
   • Hormones
     • stress is important & increases cortisol
       • 20% women report postpartum depression
         • suspect hormonal fluctuations are contributing factor
         • 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
       • declining level of hormone testosterone assoc. with increased prob of sep
     • few studies have links hormones to dep & rship remains uncertain

3. Abnormalities of Hemispheric Dominance

   • normal people found strong rship between happy mood and increased activity in left prefrontal cortex
     • JACOBS & SNYDER 1996
     • Dep people decreased activity in left and increased activity in right prefrontal cortex
       • this imbalance is stable over years despite changes in symptoms of depression
   • Most people gaze to the right during verbal tasks but dep gaze left showing right-hemisphere dominance
     • LENHART & KATKIN 1986

4. people with major depression feel sad, helpless everyday for weeks at a time

   • feel worthless have little energy
   • absence of happiness is more reliable symptom than increased sadness
   • decreased response to happy facial expressions and decreased response to a likely reward
     • MONK ET AL 2009
   • standards for diagnosis vary - no lab tests to confirm diagnosis to stats vary
   • depression in childhood is equal for boys and girls
     • 14+ its more common in females
       • TWENGE & NOLEN-HOCKSEMA 2002
   • Most people suffer from episodes separated by periods of normal moods.
     • rat episode is longest and triggered by an event