The Nature vs Nurture Debate: Nature
Depression
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Caspi used subjects from a lifelong observational study of Caucasian New
Zealanders known as the Dunedin Multidisciplinary Health and Development Study.
This cohort of 1037 children was studied at ages 3, 5, 7, 9, 11, 13, 15, 18, and 21,
and 96% of the subjects could still be found to answer questions at the age of 26.
847 members of the cohort were divided into three groups based on 5-HTTLPR
genotype. Humans are subdivided into three types based on this gene: SS, LL, and
SL.
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In Caucasian populations, about 20% are SS, 30% are LL, and 50% are SL.
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This gene is the promoter region for the serotonin transporter, which means this
gene determines how many serotonin transporters you have. Serotonin is an
important neurotransmitter in regulating our emotional state.
People with the LL gene have more serotonin and people with the SS gene have less
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With no abuse, the SS, LL, and SL genotypes all have a similar lifetime risk of
developing depression. Once you add childhood abuse, though, the LL genotype still
has about the same risk as with no abuse, while the SL and SS risk climbs
dramatically, showing that nature plays a significantly bigger role in developing
depression than nurture.
Addiction

Research highlighted by the National Institute on Alcohol Abuse and Alcoholism
suggests that people of Asian decent have a specific type of gene that makes the
experience of alcohol unpleasant. For people with this gene, drinking alcohol means
feeling flush and faint, and perhaps slightly nauseated. People like this may not
develop alcoholism, because they don’t drink a significant amount.
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Research published in the journal Alcoholism: Clinical and Experimental Research
suggests that some people have a gene variant that allows signals of pleasure to
move quickly from one portion of the brain to the other, when alcohol is in play.
People like this are more vulnerable to the behavioral changes alcohol can bring, so
one little sip causes a big shift in the way they feel and the manner in which they
act.

The American Psychological Association states that “at least half of a person’s
susceptibility to [addiction] can be linked to genetic factors”. As a matter of fact,
research studies indicate that the children of addicts are 8 times more likely to
develop an addiction of some sort at some point during their lifetime.