Mood disorders

Mood disorders are a class of mental disorders characterized by sustained disturbances in emotional state, including depressive disorders (major depressive, persistent depressive, premenstrual dysphoric, disruptive mood dysregulation) and bipolar disorders (Bipolar I, Bipolar II, cyclothymic).

Overview

Mood disorders are a class of mental disorders characterized by sustained disturbances in emotional state that produce clinically significant distress or impairment. The DSM-5-TR organizes them into two principal chapters: Depressive Disorders (major depressive disorder, persistent depressive disorder, premenstrual dysphoric disorder, disruptive mood dysregulation disorder, substance/medication-induced depressive disorder, depressive disorder due to another medical condition) and Bipolar and Related Disorders (Bipolar I disorder, Bipolar II disorder, cyclothymic disorder, substance/medication-induced bipolar and related disorder, bipolar and related disorder due to another medical condition).

Mood disorders are among the most common mental health conditions. Lifetime prevalence: major depressive disorder approximately 17-20% in Canadian adults; persistent depressive disorder approximately 1.5-2%; bipolar I disorder approximately 1%; bipolar II disorder approximately 1%. Mood disorders are more common in women than men for depression (approximately 2:1 ratio); bipolar disorders affect men and women approximately equally.

The boundary between depressive and bipolar disorders is clinically critical. Many individuals presenting with depression have undiagnosed bipolar disorder; antidepressant monotherapy in unrecognized bipolar depression can precipitate switches to mania, mixed states, or rapid cycling. Careful history-taking for past hypomania or mania is essential in any depressive presentation.

Mood disorders are highly comorbid with anxiety disorders, substance use disorders, ADHD, eating disorders, and personality disorders. Suicide risk is elevated across mood disorders and substantially elevated in severe presentations, mixed states, and the early course of bipolar disorder.

Treatment is highly effective. Evidence-based options include psychotherapy (CBT, IPT, behavioural activation, MBCT, CBASP, IPSRT), pharmacotherapy (SSRIs, SNRIs, mood stabilizers, atypical antipsychotics), neurostimulation (ECT, rTMS), and combined approaches. Most people with mood disorders achieve substantial improvement with appropriate treatment.

Signs and symptoms

Persistent low mood (depression) — Sustained sad, empty, or hopeless mood most of the day, more days than not.
Anhedonia — Markedly diminished interest or pleasure in activities, particularly things normally enjoyed.
Sleep changes — Insomnia (typically with depression) or hypersomnia (with atypical depression or some bipolar episodes).
Appetite and weight changes — Significant change in appetite or weight, in either direction.
Energy and activity changes — Fatigue (depression) or markedly increased energy and activity (mania/hypomania).
Cognitive changes — Difficulty concentrating, indecisiveness, slowed thinking (depression) or racing thoughts, distractibility (mania/hypomania).
Self-evaluation changes — Persistent worthlessness or excessive guilt (depression) or grandiosity, inflated self-esteem (mania).
Suicidal ideation — Thoughts of death, suicidal ideation, plans, or attempts — particularly in severe depression and mixed states.
Mania/hypomania — Elevated, expansive, or irritable mood with increased goal-directed activity, decreased need for sleep, and other characteristic features.
Psychotic features — Mood-congruent or mood-incongruent delusions or hallucinations in severe episodes.

Diagnostic context

The DSM-5-TR mood disorder classes have specific diagnostic criteria for each disorder. The principal diagnoses:

Major Depressive Disorder (296.2x/296.3x): 5+ of 9 symptoms (including either depressed mood or anhedonia) most of the day, nearly every day, for at least 2 weeks, causing significant distress or impairment, not better explained by another condition.

Persistent Depressive Disorder (300.4): chronic depressed mood for at least 2 years (1 year in youth) with at least 2 additional symptoms; combines former Dysthymic Disorder and Chronic MDD.

Bipolar I Disorder (296.4x-296.7): at least one full manic episode (≥1 week of elevated/irritable mood + 3+ associated symptoms causing marked impairment).

Bipolar II Disorder (296.89): at least one hypomanic episode (≥4 days, less severe than mania) and at least one major depressive episode, never a full manic episode.

Cyclothymic Disorder (301.13): 2+ years (1+ year in youth) of subthreshold hypomanic and depressive symptoms.

Premenstrual Dysphoric Disorder (625.4): cyclical severe mood symptoms in the luteal phase, remitting after menses.

Disruptive Mood Dysregulation Disorder (296.99): chronic severe irritability and frequent temper outbursts in children, between ages 6 and 18.

Specifiers across mood disorders include: with anxious distress; with mixed features; with melancholic features; with atypical features; with mood-congruent or mood-incongruent psychotic features; with catatonia; with peripartum onset; with seasonal pattern; with rapid cycling (bipolar). Detailed diagnostic information is provided on the depression, persistent-depressive-disorder, and bipolar-disorder specialty pages.

Causes and risk factors

Mood disorders develop through interaction of biological, psychological, and social factors:

Genetic factors: heritability of major depressive disorder approximately 30-40%; bipolar disorder 60-85%. Family history is one of the strongest individual risk factors.

Neurobiological factors: alterations in monoaminergic systems (serotonin, norepinephrine, dopamine), HPA axis dysfunction, neuroplasticity (BDNF, glutamate signaling), inflammation, and circadian rhythm regulation are documented across mood disorders.

Developmental factors: childhood adversity (ACE exposure), early loss, attachment disruption, and prenatal exposures (maternal depression, stress, substances) all elevate risk.

Psychological factors: negative cognitive patterns (rumination, catastrophizing, negative attribution style), low self-esteem, perfectionism, and certain personality features (high neuroticism) all elevate risk.

Social and environmental factors: chronic stress, trauma, loss, social isolation, poverty, discrimination, and limited social support all contribute. Major life transitions (relationship loss, job loss, illness, major moves) often precipitate episodes.

Trigger factors: sleep deprivation, jet lag, postpartum period, antidepressant use without mood stabilizer (in bipolar), substance use (especially stimulants and cannabis), and major stressors can precipitate episodes in vulnerable individuals.

Comorbidity: anxiety disorders, substance use disorders, ADHD, eating disorders, and personality disorders are all commonly comorbid. Approximately 60-80% of individuals with mood disorders have at least one comorbid condition.

Typical treatments

Treatment varies by specific mood disorder and presentation. Evidence-based approaches include:

Psychotherapy:

Cognitive behavioural Therapy — strong evidence for depression, anxiety, and as adjunct for bipolar disorder.
Interpersonal Psychotherapy (IPT) — strong evidence for depression, particularly perinatal depression.
behavioural Activation — effective stand-alone or component intervention for depression.
Mindfulness-Based Cognitive Therapy (MBCT) — relapse prevention for recurrent depression.
Cognitive behavioural Analysis System of Psychotherapy (CBASP) — chronic depression.
Interpersonal and Social Rhythm Therapy (IPSRT) — bipolar disorder.
Family-Focused Therapy — bipolar disorder, particularly adolescent presentations.
Dialectical behaviour Therapy (DBT) — when borderline features or self-harm is present.

Pharmacotherapy:

SSRIs and SNRIs — first-line for depression and most anxiety disorders.
Mood stabilizers (lithium, valproate, lamotrigine) — bipolar disorder.
Atypical antipsychotics — bipolar disorder, treatment-resistant depression.
Antidepressant + mood stabilizer combinations for bipolar depression (avoid antidepressant monotherapy).
Specialized agents (esketamine, ketamine, brexanolone) for treatment-resistant or specific presentations.

Neurostimulation: ECT for severe treatment-resistant depression, mania, and mixed states; rTMS for treatment-resistant depression; emerging evidence for DBS and other modalities.

Combined treatment (psychotherapy + pharmacotherapy) outperforms either alone for moderate-to-severe presentations.

Lifestyle interventions: regular sleep-wake schedule (particularly important in bipolar disorder), physical activity (effective for mild-moderate depression), light therapy (seasonal pattern), nutritional support.

Crisis intervention when suicide risk is elevated.

Detailed treatment information for specific disorders is on the depression, persistent-depressive-disorder, bipolar-disorder, and seasonal-affective-disorder specialty pages.

When to seek help

Professional support is indicated when:

You experience persistent low mood, anhedonia, or other depressive symptoms lasting two or more weeks.
You experience periods of unusually elevated mood, decreased need for sleep, racing thoughts, or impulsive behaviour.
Symptoms interfere with work, relationships, or daily functioning.
You are experiencing suicidal thoughts, plans, or self-harm urges.
Mood symptoms have a clear seasonal or cyclical pattern.
You are pregnant, postpartum, or experiencing premenstrual mood changes that are severe.
You have been treated for depression with antidepressants without sustained improvement, or with worsening over time.

If suicidal thoughts are present, free 24-hour support is available across Canada at 9-8-8 (Suicide Crisis Helpline, call or text), 1-833-456-4566 (Talk Suicide Canada), or 811 (Health Link).

Frequently asked questions

How is depression different from sadness?

Sadness is a normal emotion in response to loss or difficulty; major depressive disorder is a clinical condition involving sustained low mood plus other symptoms (sleep, appetite, energy, concentration, self-evaluation, suicidal ideation), causing significant impairment, lasting weeks or longer.

How do I know if I have depression or bipolar disorder?

The key distinction is whether you have ever experienced a manic or hypomanic episode (elevated mood, decreased need for sleep, racing thoughts, increased activity, risky behaviour). Many people with bipolar disorder are initially diagnosed with depression because they only seek help during depressive episodes; careful history-taking for past elevated periods is essential.

Are antidepressants addictive?

No. SSRIs and other antidepressants do not produce dependence in the addictive sense — they do not cause craving, do not produce a "high," and discontinuation does not produce a withdrawal syndrome that drives compulsive use. Discontinuation can produce uncomfortable symptoms (discontinuation syndrome) which is managed by gradual tapering.

How long does treatment take?

For acute depression, response typically appears in 2-6 weeks of medication or therapy; full remission often takes 8-12 weeks. Maintenance treatment for 6-12 months is recommended after first episode; longer for recurrent depression. Bipolar disorder typically requires long-term maintenance treatment.

Will I have to take medication forever?

For first episode of major depressive disorder, many people successfully discontinue medication after 6-12 months of stable remission. Recurrent depression often requires longer maintenance. Bipolar disorder usually requires long-term maintenance to prevent relapse. Decisions are individualized in collaboration with prescriber.

Can I treat mood disorder without medication?

For mild-to-moderate depression, psychotherapy alone (particularly CBT, IPT, behavioural activation) is often sufficient. For severe depression, severe persistent depression, and bipolar disorder, combined psychotherapy and pharmacotherapy generally produces better outcomes than therapy alone.

References

American Psychiatric Association. (2022). Diagnostic and Statistical Manual of Mental Disorders (5th ed., text rev.). APA.
Lam, R. W., et al. (2016). Canadian Network for Mood and Anxiety Treatments (CANMAT) 2016 clinical guidelines for the management of adults with major depressive disorder. Canadian Journal of Psychiatry, 61(9), 510–523.
Yatham, L. N., et al. (2018). CANMAT and ISBD 2018 guidelines for the management of patients with bipolar disorder. Bipolar Disorders, 20(2), 97–170.
Cuijpers, P., et al. (2014). Adding psychotherapy to antidepressant medication in depression and anxiety disorders: A meta-analysis. World Psychiatry, 13(1), 56–67.
Goodwin, F. K., & Jamison, K. R. (2007). Manic-Depressive Illness: Bipolar Disorders and Recurrent Depression (2nd ed.). Oxford University Press.

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