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's symptoms are consistent with “bipolar disorder,” which includes alternating between periods of depression and mania. By definition, a manic episode must last at least one week and not be induced by drugs or alcohol. Even though Sarah experiences periods of “depression,” bipolar disorder is the more appropriate diagnosis due to her manic episodes. “Borderline personality disorder” includes symptoms related to instability in relationships, emotions, and self-image. “Generalized anxiety disorder” is characterized by excessive anxiety regarding a number of things that induces impaired functioning. Last, “schizophrenia” is a psychotic disorder that involves at least two of the following symptoms: hallucinations, delusions, disorganized thinking, disorganized behavior, and emotional flattening.

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.