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

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

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.

People with major depressive disorder typically give up their productivity and their motivation to complete daily tasks. Below is a comprehensive list of some of the most common symptoms of major depressive disorder.

When people are living with major depressive disorder, they experience emotional symptoms (feeling sad and dejected), motivational symptoms (loss of desire to pursue usual activities and duties), behavioral symptoms (feeling less active and less productive), cognitive symptoms (holding negative views of self, like feeling inadequate, undersireable, inferior, worthy of blame), and physical symptoms (experiencing headaches, indigestion, constipation, dizzy spells, and general pain).

Preoccupation with schedules and productivity is more indicative of an obsessive-compulsive disorder than a depressive disorder.

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.

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.

Affective disorders are defined by heightened and prolonged emotional states. In the instance of anxiety, which can manifest in many forms, one experiences a consistent state of fear that may or may not have a specific set of triggers. Depression is a prolonged state of sadness and apathy, which often involves a general lack of motivation or pleasant emotions, irritability, difficulty focusing, and, in extreme cases, suicidal thoughts. Bipolar disorder includes this kind of depressive state, yet also a manic one. During the manic state, there is a general feeling of euphoria, an "on top of the world" kind of feeling that may invite impulsive decision-making and an inflated sense of self-importance.

Psychological disorders that are not affective have to do with delusional thinking patterns, personality, attention deficits, addictions, psychosexuality, or developmental problems. While they may share commonalities and even intersect, affective disorders have distinctly to do with prolonged and extreme emotional states, which can be caused by biological or environmental factors.

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.

Dysthymic disorder is a mood disorder that is similar to, but longer-lasting and less disabling, than major depressive disorder. It is diagnosed after at least two years of on-going, mild symptoms of unipolar depression.

Dsythymia and major depressive disorder are both mood disorders, specifically focused on depressive symptomology. The main difference between them is that dsythymia is a low grade depression that lasts multiple years, while major depressive disorder is a single, severe depressive episode.