Depression (Major Depressive Disorder) is a common and serious medicalillness that negatively affects how one feels, the way one thinks and how one acts. Depression causes feelings of sadness and/or a loss of zest in doing activities once enjoyedbyavictim.Itcanleadtoavarietyofemotionalandphysicalproblemsandcan decrease a person?s productivity and efficiency at work and at home thereby bringing one?s mental and physical health down. Environmental factors play a very prominent role in causing depression apart from neuro-biological and genetic factors. There are a numberoffactorssuchaspollution,childhoodabuse,longtermstress,traumaticevents that could lead to Major Depressive Disorder(MDD). There are also ?depression genes?. Some diseases are caused by single defective gene such as cystic fibrosis or Huntington?s disease. However depression is also influenced by several genes rather than caused by a single gene. In these conditions there are combinations of genetic changes that can cause depression. Nevertheless the etiological and psycho-biological complexity of depression makes it difficult for identifying the specific genetic factors and hence it continuous to be among the last frontiers of gene hunting. Some other queer factors leading to depression are Oedipus Complex, Genetic Sexual Attraction (GSA), and having different sexual orientation(LGBTQ). In this paper the authorsfirst try to explore the various causes of depression using a database of patients suffering fromclinicaldepression.Depressionisavastarena.Weasyoungresearchershavetried to narrow down our focus mainly on patients suffering from clinical depression;trying to figure out the most common reason behind it. Our survey therefore focuses on genetic and environmental (post-rape trauma, chronic stress, childhood abuse, allergy) causes of depression. Our purpose is to give a better understanding to the cause of depression to the patients so that they can avoid it. Thereby the paper tries to statistically define the most prominent cause of Major Depressive Disorder.