Depressive & Bipolar Disorders
Counting symptoms, days and years to name the mood disorder
Major depression and its specifiers
Major depressive episode. At least five of nine symptoms are present nearly every day for at least 2 weeks, and one must be depressed mood or anhedonia. The others are sleep disturbance (insomnia or hypersomnia), guilt or worthlessness, low energy, poor concentration or indecisiveness, appetite or weight change, psychomotor retardation or agitation, and recurrent thoughts of death or suicide; SIG E CAPS lists the eight besides depressed mood. Symptoms must cause distress or impairment and not be explained by a substance or a medical condition such as hypothyroidism.
Major depressive disorder (MDD) requires one or more such episodes and no lifetime manic or hypomanic episode; a single manic episode reclassifies the illness as bipolar I.
| Specifier | Defining features | Clinical note |
|---|---|---|
| Melancholic | Anhedonia with no mood reactivity, worse in the morning, early-morning awakening, anorexia or weight loss, marked psychomotor change, excessive guilt | Most closely tied to HPA hyperactivity |
| Atypical | Mood reactivity plus hypersomnia, hyperphagia or weight gain, leaden paralysis, long-standing interpersonal rejection sensitivity | Historically MAOI-responsive; SSRIs now first-line |
| Psychotic features | Usually mood-congruent delusions of guilt, poverty, nihilism or bodily decay | Antidepressant plus antipsychotic, or ECT |
| Seasonal pattern | Recurrent fall or winter onset with spring remission | Bright-light therapy |
| Peripartum onset | Onset during pregnancy or within 4 weeks after delivery | See postpartum disorders below |
Persistent depressive disorder and PMDD
Persistent depressive disorder (dysthymia). Depressed mood on most days for at least 2 years (1 year in children and adolescents), with at least two depressive symptoms and no symptom-free interval longer than 2 months. A superimposed major depressive episode is called double depression.
Premenstrual dysphoric disorder (PMDD). In most cycles, at least five symptoms appear in the final week before menses, improve within a few days after menstruation begins and are minimal in the week after. At least one is affective (lability, irritability, depressed mood, anxiety), joined by symptoms such as fatigue, poor concentration, food cravings, sleep change, bloating or breast tenderness, with impairment. Diagnosis requires prospective daily ratings over at least two cycles. SSRIs, given continuously or only in the luteal phase, are first-line; drospirenone-containing oral contraceptives are an alternative.
Neurobiology of depression
Monoamine hypothesis. Depression is associated with reduced serotonin, norepinephrine and dopamine signaling. Antidepressants raise synaptic monoamines within hours, yet mood improves only after about 4–6 weeks, pointing to slower adaptations such as receptor downregulation and BDNF-dependent neuroplasticity. Low CSF 5-HIAA, the main serotonin metabolite, is linked to impulsive and violent suicide attempts, and imaging shows reduced hippocampal volume in recurrent depression.
HPA axis. Hypothalamic CRH and cortisol are elevated, and many patients, especially those with melancholic features, fail to suppress cortisol after dexamethasone.
Sleep architecture. REM latency is shortened, REM density and REM in the first half of the night increase, slow-wave (N3) sleep decreases, sleep latency lengthens and sleep is fragmented, ending in early-morning (terminal) awakening. Most antidepressants suppress REM sleep.
Bipolar spectrum
Manic episode. Abnormally and persistently elevated, expansive or irritable mood with increased energy lasting at least 1 week (any duration if hospitalization is needed), plus at least three symptoms (four if mood is only irritable): distractibility, risky pleasure-seeking such as spending sprees or sexual indiscretion, grandiosity, flight of ideas, increased goal-directed activity or agitation, decreased need for sleep and pressured speech (DIG FAST). Mania causes marked impairment, psychosis or hospitalization.
Hypomanic episode. The same symptoms for at least 4 consecutive days, producing a change others can observe but without marked impairment, psychosis or hospitalization; any of these upgrades the episode to mania.
| Diagnosis | Episodes required | Duration rule |
|---|---|---|
| Bipolar I | ≥1 manic episode; depression common but not required | Mania ≥1 week or any length with hospitalization |
| Bipolar II | ≥1 hypomanic plus ≥1 major depressive episode; never mania | Hypomania ≥4 days; depression ≥2 weeks |
| Cyclothymic disorder | Many hypomanic-symptom and depressive-symptom periods that never meet episode criteria | ≥2 years (1 in youth); never symptom-free >2 months |
| Persistent depressive disorder | Chronic depressive symptoms, with or without superimposed episodes | ≥2 years (1 in youth); never symptom-free >2 months |
Course. Bipolar II is dominated by depressive time. Rapid cycling means at least four mood episodes within 12 months; it is more common in women and is linked to hypothyroidism and antidepressant exposure.
Antidepressant monotherapy can switch unrecognized bipolar depression into mania or hypomania (without the hyperthermia and clonus of serotonin syndrome), or induce rapid cycling. Screen every depressed patient for past manic symptoms and family history before starting an SSRI. A manic episode that persists beyond the drug's physiologic effect establishes bipolar I. Bipolar depression is treated with lithium or specific antipsychotics such as quetiapine or lurasidone rather than an antidepressant alone.
Postpartum disorders and grief
| Feature | Blues | Depression | Psychosis |
|---|---|---|---|
| Frequency | ~50–80% of mothers | ~10–15% | ~1–2 per 1,000 |
| Timing | Starts days 2–3, resolves within 2 weeks | Onset in pregnancy or the weeks after delivery; lasts ≥2 weeks | Abrupt, within the first weeks |
| Features | Tearfulness, lability, anxiety; function intact | Full major depressive episode | Delusions, hallucinations, confusion; strongly linked to bipolar disorder |
| Management | Reassurance and support | Psychotherapy, SSRIs | Emergency hospitalization (infanticide and suicide risk) |
Normal grief. Sadness comes in waves triggered by reminders of the deceased, self-esteem is preserved, and guilt centers on things done or not done for the deceased. Briefly hearing or sensing the deceased can be normal, and functioning steadily returns.
MDD during bereavement. DSM-5 removed the bereavement exclusion, so MDD is diagnosed whenever full criteria are met. Clues are pervasive low mood not tied to reminders, global worthlessness, psychomotor retardation, marked impairment and suicidal thoughts beyond a wish to join the deceased.
Prolonged grief disorder. At least 12 months after a death (6 months in children and adolescents), intense yearning for or preoccupation with the deceased persists nearly every day, with symptoms such as identity disruption, disbelief, avoidance of reminders, emotional numbness, meaninglessness or loneliness, and impairment beyond cultural norms.
Suicide risk
Strongest predictor. A previous suicide attempt. Other major risk factors:
- Male sex: women attempt more often, but men die by suicide several times as often, largely through more lethal means.
- Older age: rates are highest in elderly white men.
- Firearm access: firearms are the most common method in the United States.
- Illness: alcohol and other substance use, depression, bipolar disorder, schizophrenia, hopelessness and chronic painful illness.
- Isolation: living alone, divorced, widowed or unemployed.
- Recent psychiatric discharge: the weeks after leaving the hospital carry especially high risk.
Energy often returns before mood as an antidepressant starts working, so suicide risk can rise early in treatment; antidepressants carry a boxed warning for suicidality in patients younger than 25. Asking directly about suicide does not increase risk.