Hockenbury Discovering Psychology 5th txtbk

550 CHAPTER 13 Psychological DisordersExplaining Mood DisordersMultiple factors appear to be involved in the development of mood disorders. First,family, twin, and adoption studies suggest that some people inherit a genetic predisposition,or a greater vulnerability, to mood disorders. Researchers have consistentlyfound that both major depression and bipolar disorder tend to run in families(Leonardo & Hen, 2005). And twin studies have shown that major depression hasa strong genetic component (Levinson, 2009; Kendler & others, 2006).A second factor that has been implicated in the development of mood disordersis disruptions in brain chemistry. Since the 1960s, several medications, called antidepressants,have been developed to treat major depression. In one way or another,the antidepressants seem to lift the symptoms of depression by increasing the availabilityof two neurotransmitters, norepinephrine and serotonin, in the brain.Abnormal levels of another neurotransmitter may also be involved in bipolar disorder.For decades, it’s been known that the drug lithium effectively alleviates symptomsof both mania and depression. Apparently, lithium regulates the availability ofCRITICAL THINKINGDoes Smoking Cause Depression and Other Psychological Disorders?Are people with a mental disorder morelikely to smoke than other people? ResearcherKaren Lasser and her colleagues(2000) assessed smoking rates in Americanadults with and without psychological disorders.Lasser found that people with mentalillness are nearly twice as likely to smokecigarettes as people with no mental illness.Here are some of the specific findings fromLasser’s study:• Forty-one percent of individuals with acurrent mental disorder are smokers, ascompared to 22 percent of people whohave never been diagnosed with a mentaldisorder.• People with a mental illness are morelikely to be heavy smokers, consuming apack of cigarettes per day or more.• People who have been diagnosed withmultiple mental disorders have higher rates of smoking andsmoke more heavily than people with fewer mental disorders(see the graph on the next page).• Forty-four percent of all cigarettes smoked in the United Statesare consumed by people with one or more mental disorders.What can account for the correlation betweensmoking and psychological disorders?Subjectively, smokers often report that theyexperience better attention and concentration,increased energy, lower anxiety, andgreater calm after smoking, effects that areprobably due to the nicotine in tobacco. So,one possible explanation is that people witha mental illness smoke as a form of selfmedication.Notice that this explanation assumesthat mental illness causes people tosmoke.Nicotine, of course, is a powerful psycho -active drug. It triggers the release of dopamineand stimulates key brain structuresinvolved in producing rewarding sensations,including the thalamus, the amygdala, andthe nucleus accumbens (Le Foll & Goldberg,2007; Salokangas & others, 2000; Stein &others, 1998). Nicotine receptors on differentneurons also regulate the release of other important neurotransmitters,including serotonin, acetylcholine, GABA, and glutamate(McGehee & others, 2007; Quattrocki & others, 2000). Inother words, nicotine affects multiple brain structures and altersthe release of many different neurotransmitters. These sameN. accumbens AmygdalaThalamusNicotine’s Effects in the Brain After cigarettesmokers were injected with up to two milli -grams of nicotine, researchers used functionalmagnetic resonance imaging to trackthe brain areas activated, which included thenucleus accumbens, the amygdala, and thethalamus. Previous research has shown thatthese brain structures produce the reinforcing,mood-elevating properties of otherabused drugs, including cocaine, amphetamines,and opiates (Stein & others, 1998).