A major depressive episode (MDE) is a mood episode upon which a diagnosis of major depressive disorder (MDD) is based. Symptoms of an MDE can arise in three areas: affect, behavior, and cognition. Most people who have an MDE return to their premorbid level of functioning after the episode, but some people will have symptoms that do not completely resolve, even after several years.
Depression is becoming increasingly prevalent in younger cohorts. Depression and anxiety disorders have a high comorbidity—around 50%.
MDD may arise with psychotic features.
In some cases, depression is related to pregnancy and giving birth (peripartum onset) or to seasonal changes in light.
A diagnosis of persistent depressive disorder requires fewer symptoms than does a diagnosis of MDD; however, the symptoms of persistent depressive disorder must persist for at least 2 years.
Neurological factors related to depression include low levels of activity in the frontal lobes, and abnormal functioning of various neurotransmitters (dopamine, serotonin, and norepinephrine). The stress–diathesis model of depression highlights the role of increased activity of the HPA axis and of excess cortisol in the blood. Genes can play a role in depression, perhaps by influencing how a person responds to stressful events, which in turn affects the activity of the HPA axis.
Psychological factors that are associated with depression include a bias toward paying attention to negative stimuli, dysfunctional thoughts, rumination, a negative attributional style, and learned helplessness.
Social factors that are associated with depression include stressful life events, social exclusion, and problems with social interactions or relationships. Culture and gender can influence the specific ways that symptoms of depression are expressed.
Neurological, psychological, and social factors can affect each other through feedback loops, as outlined by the stress–diathesis model and Coyne’s interactional theory of depression. According to the stress–diathesis model, abuse or neglect during childhood (a stressor) and increased activity in the HPA axis can lead to overreactive cortisol-releasing cells (a diathesis), which respond strongly to even mild stressors. Psychological factors can create a cognitive vulnerability to depression, which in turn can amplify the negative effects of a stressor and change social interactions. Coyne’s theory proposes that among neurologically vulnerable people, their depression-related behaviors may alienate other people, producing social stressors.
Biomedical treatments that target neurological factors for depressive disorders are medications (SSRIs, TCAs, MAOIs, SNRIs, NaSSAs) and St. John’s wort, and brain stimulation (ECT or TMS).
Treatments for depression that target psychological factors include CBT (particularly with behavioral activation).
Treatments that target social factors include IPT and systems therapy.
Bipolar Disorders
The three types of mood episode that underlie bipolar disorders are major depressive episode (MDE), manic episode, and hypomanic episode. Symptoms of a manic episode include grandiosity, pressured speech, flight of ideas, distractibility, poor judgment, decreased need for sleep, and psychomotor agitation. A hypomanic episode involves mood that is persistently elated, irritable, or euphoric; unlike other mood episodes, hypomanic episodes do not impair functioning.
There are two types of bipolar disorder: Bipolar I disorder—usually more severe—requires only a manic episode; an MDE may occur but is not necessary for this diagnosis. Bipolar II disorder requires alternating hypomanic episodes and MDEs and no history of manic episodes. Cyclothymic disorder is a more chronic but less intense version of bipolar II disorder.
Neurological factors that are associated with bipolar disorders include an enlarged and more active amygdala. Norepinephrine, serotonin, and glutamate are also involved. Bipolar disorders are influenced by genetic factors, which may affect mood disorders in general.
Psychological factors that are associated with bipolar disorders include the cognitive distortions and negative thinking associated with depression.
Social factors that are associated with bipolar disorders include disruptive life changes and social and environmental stressors. The different factors create feedback loops that can lead to a bipolar disorder or make the patient more likely to relapse.
Treatments that target neurological factors include medications that act as mood stabilizers, such as lithium and anticonvulsants. When manic, patients may receive an antipsychotic medication or a benzodiazepine. Patients with a bipolar disorder who have MDEs may receive an antidepressant along with a mood stabilizer.
Treatment that targets psychological factors—particularly CBT—helps patients recognize warning signs of mood episodes, develop better sleeping strategies, and, when appropriate, stay on medication.
Treatments that target social factors include interpersonal and social rhythm therapy (IPSRT), family therapy, and group therapy or a self-help group.
Suicide
Suicide is ranked 10th among causes of death in North America. Having thoughts of suicide or making a plan to carry it out may indicate a risk for suicide; certain behavioral changes (such as giving away possessions) may indicate a more serious risk. However, not everyone who attempts or commits suicide displays warning signs. In addition, certain types of self-harm may be parasuicidal behaviors rather than suicide attempts. The presence of certain psychological disorders, such as MDD, and a history of previous serious suicide attempts increase a person’s risk for suicide.
Neurological factors that are associated with suicide include altered serotonin activity and a genetic predisposition. Psychological risk factors for suicide include poor coping and problem-solving skills, distorted and rigid thinking, and a sense of hopelessness. Variations in suicide rates across countries point to a relationship between social factors and suicide.
Crisis intervention efforts to prevent suicide first ensure that the suicidal person is safe and then help the person see past the hopelessness and rigidity that pervade his or her thinking. Longer-term suicide prevention may also help the patient to identify the stressors that led him or her to feel suicidal and develop new solutions to the problems.