Describe Major Depressive Disorder, highlighting the neurochemical and Essay

Describe Major Depressive Disorder, highlighting the neurochemical and physical changes that are associated with this disease. Based on the known neurochemical - Essay Example The importance of MDD lies in the fact that it causes considerable impairment in social functioning, role functioning, employment and physical health of the afflicted person (Wells et al, 1989). Experts are of the opinion that depression is actually a heterogeneous syndrome comprised of numerous diseases of distinct causes and pathophysiologies (Nestler et al, 2002). MDD is also known as clinical depression or unipolar depression. According to the National Comorbidity Survey Replication (NCS-R),  which studied the epidemiology of MDD across the United States, the prevalence of MDD for lifetime was estimated as 16.2% and that for 12-month was estimated as 6.6% (Kessler et al, 2003). There are very few studies which relate the prevalence of MDD to race or ethnicity (table-2). Infact, severe forms of depression affect 2-5% of the US population (Nestler et al, 2002). As far as age is considered, the risk is fairly low in the younger age groups (Figure-1). While major depressive disorder can develop at any age, the median age at onset is 32 (Kessler et al, 2005). It is more prevalent in women than in men (Kessler et al, 2003). MDD is comorbid with anxiety and substance use disorders (Kessler et al, 2003). Studies have shown that MDD with anger attacks are significantly associated with increased cholesterol levels and years of smoking (Fraquas et al, 2007). MDD is a debilitating and complex psychiatric disorder that involves multiple neural circuits and genetic and non-genetic risk factors (Sahay et al, 2007). Whether environmental factors or genetic factors play a major role in the pathogenesis of MDD is still debated. Exaggerated early error-detection processes have been incriminated in the etiology and maintenance of major depressive disorder and thus such processes may then recruit excessive neural and cognitive resources that manifest as symptoms of depression (Chiu and Deldin,