evolutionary perspective of mental disorders

Kretschmer (1970) observed that bipolar disorder is associated with a pyknic physique. The large trunk compared to the arm and leg length would mean that their body was good for body heat conservation during the times of extreme cold winters. Therefore when clothes and use of fire were introduced, there was so need for the pyknic physique, therefore gives reasoning why the bipolar genes died out quite early in ancestral history. Sherman (2001) states that mania was an adaptive response when faced with emergencies and physical challenges. When there was a lack of food and sleep, having the strength produce from the manic behaviour would have been an advantage. We have developed the experience of loss of status back in the EEA to for example an ending of a relationship. However become depressed over such reasons is not likely to be effective like the way it was intended. A genome lag has occurred meaning that our brains are still adaptive to the EEA, rather than our modern society.

There is a distinction between general anxiety, which has evolved as an emotional response to situations in which the threat could not be identified, and specific anxiety which has evolved to protect individuals against specifics dangers. One type of anxiety disorder we can experience is a phobia, which is an irrational fear which is out of proportion to the reality of the threat. Whilst anxiety can be adaptive, phobias can be maladaptive. Seligman (1970) stated from his preparedness argument that the phobias we experience are adaptive as they are a fear of things we would have caused danger in the time of the EEA e.g. snakes, heights and strangers. As humans we have an innate predisposition to acquire the fear responses through conditioning as we are biologically prepared to exhibit physiological and emotional responses as defence mechanisms.

Another type of anxiety disorder we experience is obsessive-compulsive disorder (OCD), whereby an individual experiences intrusive thoughts that lead them to perform ritualised behaviours. Such rituals include grooming and hoarding. This supports the evolutionary theory as grooming is adaptive as it smoothes social interaction and hoarding was carried out as resources were collected ready for the long severe winters, however this behaviour has now become maladaptive.

Nesse & Williams (1996) stated that we associate harm with certain stimuli more than others. For example, monkeys that were exposed to a videotape of other monkeys acting frightful to a snake will develop a phobia, whereas they do not do so for leaves and flowers. Fear is said to be negatively correlated with animals’ appearance. The animals that look least like humans elicit a stronger phobic response, Bennett-Levy & Marteau (1984). This supports the evolutionary theory as it states we are programmed to imprint on own our species and avoid unrelated species, which accepts the view that phobias are due to innate predispositions. We do also fear dangers in our modern society such as public transport and driving, 50% of the individuals who experience this phobia had been involved in a traffic accident, Barlow & Durand (1995). Mowrer (1947) stated that the two-process theory of phobias suggests they are acquired through classical conditioning and maintained through negative reinforcement. This contradicts evolutionary explanations as it shows that phobias are learned.

There is a lack of research to support the evolutionary theory during to it being post hoc. It is said that mental disorders are pathological exaggerations of normal adaptive responses. However, this may be the wrong approach as there may be a genetic basis and a defective gene may be the cause of this.