Major depressive disorder is the most common mood disorder and is characterized by a depressed mood and physical symptoms such as loss of appetite and fatigue for 2 or more weeks in the absence of a clear cause. SAD has the symptoms of major depressive disorder but the episodes occur seasonally, typically during winter. Dysthymia is similar to major depressive disorder but it is less severe and lasts longer (at least 2 years). Bipolar disorder involves episodes of both depression and mania. Minor depressive disorder is still being researched and you do not have to know it for the AP Psychology exam.

Beck's cognitive triad examines the explanations people make about themselves, their future, and their world. When something happens, someone can decide that it was either caused by them or caused by an external factor (internal/external), generalize the event to all events or keep it specific to the event at hand (global / specific), and decide whether he or she thinks it will continue in the future or will end soon (stable/unstable). When something good happens, such as a job promotion, someone who is depressed might believe the job promotion to be caused by luck (external), only because they are good at their job but nothing else (specific), and probably won't last long (unstable).

Beck's cognitive triad examines the explanations people make about themselves, their future, and their world. When something happens, someone can decide that it was either caused by them or caused by an external factor (internal/external), generalize the event to all events or keep it specific to the event at hand (global / specific), and decide whether he or she thinks it will continue in the future or will end soon (stable/unstable). If someone is depressed and they lose their job (or something else bad happens), they are likely to assume it's their fault (internal), it characterizes the fact that they can't do anything right (global), and their luck will not change (stable). 

Genetics, low serotonin, learned helplessness, and the cognitive triad are all hypothesized to be contributing factors to depression; however, excess levels of dopamine contribute to schizophrenia, not depression.

Learned helplessness is the idea that a person has learned from past experiences that they cannot control parts of their life, which can contribute to depression. Beck's cognitive triad examines the explanations people make about themselves, their future, and their world. When something happens, someone can decide that it was either caused by them or caused by an external factor (internal/external), generalize the event to all events or keep it specific to the event at hand (global / specific), and decide whether he or she thinks it will continue in the future or will end soon (stable/unstable). When someone is depressed, they tend to believe that good events are external, specific, and unstable, while bad events are internal, global, and stable.

Sarah displays all of the classic symptoms of a major depressive disorder. The fact that her condition is long-term makes it more likely to be a major depressive disorder. Generalized anxiety disorder is the persistence of a feeling of uneasiness or that something bad will occur over a long period of time, with no specific trigger. Anorexia is an eating disorder. Anemia is a decrease of oxygen in the blood.

Note that the question asks which answer option does not help explain the prevalence of depression in females. The correct answer is actually a false statement: on average, females have longer lives than males. This increased lifespan can result in a greater sense of loss and loneliness in old age, which can contribute to depressive symptoms in females. The other answer options are all considered plausible reasons that females experience depression more frequently than males.

Depression is accompanied by an overall decrease in energy, pleasure, motivation, and positive thoughts. Aggression is not a common symptom of depression.

Depressed schemas are how an individual views the world and sees events around them. They guide perceptions are tend to be negative beliefs and attitudes. In this case Sherry's therapist is focused on here "general underlying negative beliefs," which is synonymous with "depressed schemas."

Major Depressive Episode is correct, because going off of the description we do not know if Ann has had a manic episode in the past or not. In order to have Major Depressive Disorder, an individual cannot have had a manic episode in the past. The answer would not be Dysthymic Disorder, because those symptoms must persist for two years or more, and disruptive mood dysregulation disorder is characterized by outbursts of severe temper in addition to depressive symptoms. 

Low levels of serotonin or abnormalities with serotonin receptors are generally associated with depression and other mood disorders.