Wednesday, 1 April 2009


Genetic Criticisms:
  • * One weakness of the genetic explanation is that there is a problem of the nature-v-nurture argument. It is difficult to separate out the influence of nature and nurture. Whilst the twin studies provide strong evidence for the role of genetic factors and the adoption studies point to the role of nature over nurture this is not conclusive.
  • * A major criticism of the genetic explanation of depression is that most of the twins and other family members in the studies on which the evidence is based were brought up together in a common environment. Twins also share a common pre-natal environment. This is a problem because it makes it impossible to separate the effects of genetics from the effects of learning. (Behaviourists would favour the learning argument to explain depression). This suggests that perhaps the validity of twin and family studies is questionable which weakens the genetic argument.
  • * A final problem is that there is an issue with population validity. The reason for this is because the samples used in such studies are so small and therefore there is difficulty generalising the results to the rest of the population.

Biological Criticisms
  • * One strength of the biological explanation of depression is that there is further empirical support provided by Ogilvie et al. (1996). They showed that cells use a gene called SERT to make serotonin transporter protein which plays an important role in the transmission of information between neurons. In most people, part of this gene called the second intron contains 10-12 repeating sections of DNA. However, people with depression, only have 9 repeating sections of DNA. This suggests that there is wider academic support for the idea that serotonin is strongly associated with depression.
  • * One weakness of the biological explanation of depression is that there are individual differences. Not everyone who suffers from depression is helped by serotonin-based drugs, which suggests that there are other causes of the disorder. It is also not clear why some people become depressed when their serotonin or norepinephrine level is low, whereas others with the low neurotransmitter level remain depression-free. This suggests that the results gained from such research cannot be generalised to the whole population.

Biological Causes

Research suggests that people suffering from depression have imbalances of neurotransmitters, natural substances that allow brain cells to communicate with one another. Two transmitters implicated in depression are serotonin and norepinephrine. Scientists think a deficiency in serotonin may cause the sleep problems, irritability, and anxiety associated with depression. Likewise, a decreased amount of norepinephrine, which regulates alertness and arousal, may contribute to the fatigue and depressed mood of the illness.

Other body chemicals also may be altered in depressed people. Among them is cortisol, a hormone that the body produces in response to stress, anger, or fear. In normal people the level of cortisol in the bloodstream peaks in the morning, then decreases as the day progresses. In depressed people, however, cortisol peaks earlier in the morning and does not level off or decrease in the afternoon or evening.

Researchers don't know if these imbalances cause the disease or if the illness gives rise to the imbalances. They do know that cortisol levels will increase in anyone who must live with long-term stress.

Genetic Factors

Evidence: Twin Studies
Much of what we know about the genetic influence of clinical depression is based upon research that has been done with identical twins. It has been found that when one identical twin becomes depressed the other will also develop clinical depression approximately 76% of the time. When identical twins are raised apart from each other, they will both become depressed about 67% of the time. Because both twins become depressed at such a high rate, the implication is that there is a strong genetic influence.

Twin studies provide a strong argument that depression is largely biological based, however because the rate at which the twins develop depression is not 100%, then there must be other factors contributing or causing the depression, for example environment could play a role.

A Gene for Depression?

Research on the genetic causes of clinical depression has attempted to identify one or more specific genes that may lead to the development of a depressive illness. Although there have been a number of studies that appear to name a particular gene as the culprit there has been little consistency among their results. However, the outcome of some research has suggested that there may be specific genes that cause clinical depression to develop within certain families and not in others.

Treating Depression

People with otherwise untreatable depression improved in a small clinical trial after receiving continuous electrical stimulation of a part of the brain that scientists believe regulates sadness.

A report in the journal Biological Psychiatry said 12 of 20 patients with chronic major depression benefited from the electronic device. For seven of the 12, the disease went into remission. The benefits were sustained over the course of the one-year study, researchers said.

Following this research, depression seems to be biological based, as it was able to be treated biologically, as opposed to depression developing from the several other suggested causes, e.g. psychological.