Aaron beck is a psychiatrist and professor at the university of Pennsylvania. He is known as the father of cognitive therapy, and is most famous for his pioneering theories, cognitive triad theory. Beck's cognitive triad is is a triad of types of negative thought present in depression and forms part of his his Cognitive Theory Of Depression. The triad goes as so:  1.The self (i.e., self is worthless) 2.The world/environment (i.e., world is unfair), and 3.The future (i.e., future is hopeless.) the cognitive theory of depression states that depression acts as a result of maladaptive, faulty, or irrational cognitions taking the form of distorted thoughts and judgments. This dissertations can be learn socially, observational, from family or friends or from a lack in experiences having to deal with the development of adaptive coping skills. The theory suggests that with who suffer from depression have different thoughts then those who don’t, which is the main cause of their depression. Beck theory believes that negative thoughts, generated by dysfunctional beliefs are the main cause of depressive symptoms, which in turn causes you to become more depressed. Beck says that there are three dysfunctional belief themes or schemas, which dominate depressed people's thinking: 1) I am defective or inadequate, 2) All of my experiences result in defeats or failures, and 3) The future is hopeless. Together these three dysfunctional beliefs make up Negative Cognitive Triad.

Major depression is a type of depression which sadness and disinterest in once-enjoyed activities interfere with how you function every day. The DSM-IV states that someone who suffers from major depression must have depression symptoms such as loss in interesting in once enjoyed activities for at the least a two week period. Other symptoms include, feeling depressed for most of the day, nearly every day, loss or increase in apatite, insomnia or hysteria, Fatigue or loss of energy nearly every day, Recurrent thoughts of death, Feelings of worthlessness, and Diminished ability to think or concentrate. If a person has suffered from the fallowing manic, hippomanic, or mixed episodes (e.g., a bipolar disorder) or if the depressed mood is better accounted for by schizoaffective disorder and is not superimposed on schizophrenia, schizophreniform disorder, delusional disorder or psychotic disorder, or if depressed mood is caused by substances (such as drugs, alcohol, medications) the depression  is not considered to be major depressive disorder. Major depressive disorder is theorized to be caused by a combination of brain chemistry, family history, and psychosocial environment. levels of the neurotransmitters nor epinephrine, serotonin, and dopamine are closely linked with depression. It can’t be proven which of these factors is most affective, but each has it’s own risk factors. Genetics, from one parent, can affect a persons change of getting  major depression by 27% and double with both. Physical and environmental risk factors can increase the chance of a person having major depressive disorder, people who have a history of trauma, sexual abuse, physical abuse, physical disability, bereavement at a young age, alcoholism, and insufficient family structure. and the is a greater risk for Women during and within the first few months after pregnancy, called postpartum depression. Major depressive disorder affects 10% of men and 20% of women.