Major Depression Research Paper

For decades, the definition of Major Depression (MD) has been an issue, in part due to the complexity of the disorder. Issues include whether the disorder is a categorical one, in that people are either have the symptoms or not, or more of a dimensional approach, where the symptoms vary in intensity between people (Cole, McGuffin & Farmer, 2008.) For the purpose of this essay, depression is defined as a mood disorder involving emotional, motivational, behavioural, physical and cognitive symptoms (Davey, 2011). According to the Diagnostics and Statistical Manual of Mental Disorders 5th Edition (DSM V), symptoms of MD include “markedly diminished interest or pleasure in activities, insomnia or hypersomnia, feelings of worthlessness and recurrent

Depression is regularly associated with low levels of serotonin, a neurotransmitter that is responsible for many areas related to memory, sleep, appetite and learning. Selective serotonin reuptake inhibitors, which increase serotonin levels, are a class of compounds typically used to treat depression, and they are one of the most frequently prescribed antidepressants in the USA (Grohol, 2010). However, it is unclear whether depression causes a change in serotonin, or the change in serotonin levels causes depression (McIntosh 2015.) Kambeitz et al (2015) performed a meta analysis of 50 studies involving a total of 877 patients with depression and a control group of 968. The groups had a mean age of 42.8, and both neuroimaging and post mortem studies were used. They looked at the availability of serotonin transporter, which is a type of protein that transports serotonin, in both people with depression and people without depression. They found that the neuroimaging studies highlighted reduced serotonin transporter in the brains of depressed people, but the post mortem findings were inconclusive. This meta analysis support the serotonin hypothesis, and emphasises a link between the neurotransmitter and depression. However, this research was a meta analysis, and so there will be issues of methodology involving the neuroimaging as different researchers may have used different methods. The sample size, whilst large did

The chance of inheriting depression has been investigated through various twin studies, the results of which are compiled in a review ‘The Genetics of Depression’ (Levinson 2005), with heritability rates of 40%-50%. Adoption studies also provide evidence for the role of genetics (Wender et al 1986). However, there is not enough evidence to identify a single depression causing gene. Furthermore, if genetics is the only explanation, identical twins should have a 100% rate of depression for both children. Yet Kendler et al (1993) only found a concordance rate of 60.7%, suggesting that there is more than just genetics at