2. Mood Disorders

Learning Objectives

By the end of this topic, you should be able to:

• Define mood disorders and distinguish depressive disorders from bipolar and related disorders
• List the DSM-5 diagnostic criteria for a Major Depressive Episode
• Differentiate mania from hypomania and explain how this distinguishes Bipolar I from Bipolar II
• Identify common diagnostic tools used to assess mood disorders
• Compare psychotherapy and pharmacological treatment options for mood disorders
• Apply diagnostic criteria to a case scenario to identify the likely mood disorder

Quick Answer

Mood disorders are a category of psychological disorders defined by persistent, extreme disturbances in emotional state that go well beyond ordinary sadness or elation. The two main groups are depressive disorders, where mood is persistently low (e.g., Major Depressive Disorder), and bipolar disorders, where mood cycles between depressive episodes and elevated states of mania or hypomania (e.g., Bipolar I and II Disorder). Diagnosis relies on structured clinical interviews and rating scales like the PHQ-9 or Hamilton Rating Scale, checked against DSM-5 symptom, duration, and impairment criteria. Effective treatment usually combines psychotherapy (such as CBT), medication (antidepressants or mood stabilizers), and lifestyle changes — understanding these disorders is essential because they are among the leading causes of disability worldwide.

Major Depressive Disorder

Major Depressive Disorder (MDD) is diagnosed when a person experiences a Major Depressive Episode: at least five of the following symptoms present during the same two-week period, representing a change from previous functioning, with at least one symptom being depressed mood or loss of interest/pleasure (anhedonia):

• Depressed mood most of the day, nearly every day
• Markedly diminished interest or pleasure in nearly all activities
• Significant weight loss/gain or appetite change
• Insomnia or hypersomnia nearly every day
• Psychomotor agitation or retardation observable by others
• Fatigue or loss of energy nearly every day
• Feelings of worthlessness or excessive/inappropriate guilt
• Diminished ability to think or concentrate, or indecisiveness
• Recurrent thoughts of death or suicidal ideation

The symptoms must cause clinically significant distress or impairment and cannot be attributable to substance use or another medical condition. DSM-5 no longer automatically excludes a diagnosis when symptoms follow bereavement — grief and depression can co-occur, and clinicians must judge whether the presentation goes beyond what is expected for the loss.

Specifiers refine the diagnosis and guide treatment: single episode vs. recurrent, with peripartum onset (occurring during pregnancy or within four weeks postpartum), with seasonal pattern, or with psychotic features.

Real-world example: A college student stops attending lectures, sleeps 12 hours a day yet still feels exhausted, has lost 6 kg without dieting, and tells a friend "nothing matters anymore" — persisting for over a month. This pattern of anhedonia, appetite/sleep disruption, fatigue, and hopelessness meets several MDD criteria and warrants professional evaluation, especially given the mention of hopelessness, which can signal suicide risk.

Common misunderstanding: Many students describe ordinary sadness as "being depressed." Clinical depression requires the specific symptom count, two-week duration, and functional impairment — a bad week after an exam disappointment does not meet these criteria.

Bipolar Disorder

Bipolar disorders involve episodes of depression alternating with periods of abnormally elevated mood. The key distinction between subtypes rests on the severity of the "up" episode:

• Mania — elevated, expansive, or irritable mood lasting at least one week (or any duration if hospitalisation is required), with symptoms such as inflated self-esteem/grandiosity, decreased need for sleep, pressured speech, racing thoughts, distractibility, increased goal-directed activity, and risky behaviour (e.g., reckless spending, impulsive decisions). Mania causes marked impairment and may include psychotic features.
• Hypomania — a milder version of the same symptom pattern lasting at least four days, noticeable to others but not severe enough to cause marked impairment or require hospitalisation, and without psychotic features.

DSM-5 recognises three main subtypes:

• Bipolar I Disorder — requires at least one full manic episode (a depressive episode is common but not required for diagnosis)
• Bipolar II Disorder — requires at least one hypomanic episode and at least one major depressive episode, with no history of full mania
• Cyclothymic Disorder — chronic, fluctuating hypomanic and depressive symptoms that do not meet full criteria for hypomania or MDD, persisting for at least two years in adults

Why it matters: Mistaking Bipolar II for recurrent MDD is a common clinical error, because patients with Bipolar II usually seek help during depressive episodes and may not report hypomania as a problem (it can feel productive or pleasant). Prescribing antidepressants alone, without a mood stabilizer, can sometimes trigger a manic switch in bipolar patients — which is why careful history-taking about past "up" periods is essential before treatment begins.

Diagnosis

Diagnosing a mood disorder combines several sources of information:

1. Clinical interview — exploring symptom history, duration, family history, and functional impact
2. Standardised rating scales — the Beck Depression Inventory (BDI) and PHQ-9 for depression severity; the Hamilton Rating Scale for Depression (HAM-D) as a clinician-administered measure; the Young Mania Rating Scale (YMRS) for manic symptoms
3. Physical examination and lab tests — to rule out medical causes such as hypothyroidism, which can mimic depressive symptoms
4. Mood charting — tracking mood over weeks or months helps distinguish episodic bipolar patterns from persistent unipolar depression

An accurate diagnosis matters because depressive and bipolar disorders are treated differently — mood stabilizers are central to bipolar treatment, while antidepressants alone are the mainstay for unipolar depression.

Treatment Options

Most evidence-based care combines more than one approach:

Psychotherapy

• Cognitive-behavioural therapy (CBT) — identifies and restructures negative thought patterns that maintain depression
• Interpersonal therapy (IPT) — addresses relationship and role transitions linked to mood episodes
• Family-focused therapy and psychoeducation — particularly important in bipolar disorder to help patients and families recognise early warning signs of relapse

Medication

• SSRIs and SNRIs — first-line antidepressants for MDD (e.g., fluoxetine, venlafaxine)
• Mood stabilizers — lithium remains a gold-standard treatment for bipolar disorder and has evidence for reducing suicide risk; anticonvulsants like valproate are also used
• Atypical antipsychotics — sometimes used alongside mood stabilizers for acute mania or treatment-resistant depression

Lifestyle factors

• Regular sleep-wake schedules are especially important in bipolar disorder, since sleep disruption can trigger episodes
• Exercise, stress management, and reducing alcohol/substance use support recovery across mood disorders

Prevention and relapse management: Because both MDD and bipolar disorder are often recurrent, maintenance treatment, regular check-ins, and social support networks reduce the likelihood and severity of relapse.

Key Terms

Term	Definition	Related Concept
Major Depressive Episode	A 2-week period with 5+ depressive symptoms including depressed mood or anhedonia	Major Depressive Disorder
Anhedonia	Markedly diminished interest or pleasure in almost all activities	MDD symptom criteria
Mania	A period of abnormally elevated/irritable mood lasting 1+ week with marked impairment	Bipolar I Disorder
Hypomania	A milder elevated mood state lasting 4+ days without marked impairment	Bipolar II Disorder
Bipolar I Disorder	Diagnosis requiring at least one full manic episode	Mania
Bipolar II Disorder	Diagnosis requiring hypomania plus a major depressive episode, no full mania	Hypomania
Cyclothymic Disorder	Chronic subthreshold mood fluctuation lasting 2+ years	Bipolar spectrum
Mood stabilizer	Medication (e.g., lithium) used to control mood swings, especially in bipolar disorder	Pharmacotherapy
PHQ-9	A 9-item self-report scale for screening and rating depression severity	Diagnostic tools

Common Mistakes

Misconception: Bipolar disorder means rapidly switching moods within the same day.

Why it's wrong: Bipolar episodes are sustained states lasting days to weeks (hypomania: 4+ days; mania: 1+ week), not moment-to-moment mood swings. Rapid, situational mood changes are more consistent with emotional reactivity or, in some cases, Borderline Personality Disorder.

Correct understanding: Bipolar disorder involves distinct, sustained episodes of depression and mania/hypomania, each lasting days or longer.

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Misconception: Sadness and clinical depression are the same thing, just at different intensities.

Why it's wrong: While severity matters, MDD requires a specific cluster of symptoms (mood plus physical and cognitive changes) persisting for at least two weeks and causing functional impairment — not simply feeling sad, even intensely, for a short period.

Correct understanding: Clinical depression is a syndrome with defined duration, symptom count, and impairment criteria, not just an amplified version of everyday sadness.

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Misconception: Hypomania is not a problem because it can make a person feel productive and confident.

Why it's wrong: Even though hypomania feels pleasant to some, it is diagnostically significant and often precedes or accompanies depressive episodes; missing it (e.g., failing to report it to a clinician) can lead to a misdiagnosis of unipolar depression and inappropriate antidepressant-only treatment.

Correct understanding: Hypomania is a clinically meaningful mood state that must be reported and assessed, even when it does not feel distressing to the person experiencing it.

Comparison and Connections

Feature	Major Depressive Disorder	Bipolar I Disorder	Bipolar II Disorder
Core episode required	Major depressive episode	At least one manic episode	Hypomanic + major depressive episode
"Up" episode severity	None	Full mania (marked impairment)	Hypomania (no marked impairment)
Psychotic features possible	Yes, with specifier	Yes, during mania	Rare
First-line medication	SSRIs/SNRIs	Mood stabilizers (e.g., lithium), antipsychotics	Mood stabilizers, cautious antidepressant use
Risk if misdiagnosed as unipolar	N/A	Antidepressant alone may trigger mania	Antidepressant alone may trigger hypomania/mixed states

Practice Questions

Recall

1. State the minimum number of symptoms and duration required to diagnose a Major Depressive Episode. Guidance: At least 5 symptoms from the DSM-5 list, present during the same 2-week period, including depressed mood or anhedonia.

2. Name two standardized tools used to assess the severity of depression or mania. Guidance: Beck Depression Inventory (BDI), PHQ-9, Hamilton Rating Scale for Depression (HAM-D), Young Mania Rating Scale (YMRS).

Understanding

3. Explain the key symptomatic difference between mania and hypomania. Guidance: Duration (1+ week vs 4+ days) and severity — mania causes marked impairment or requires hospitalisation and can include psychotic features; hypomania does not.

4. Explain why treating Bipolar II Disorder with an antidepressant alone can be risky. Guidance: Antidepressants without a mood stabilizer can trigger hypomanic or mixed episodes in bipolar patients; mood stabilizers address the underlying cyclical pattern.

Application

5. A 24-year-old reports two weeks of low mood, loss of interest in hobbies, poor sleep, and difficulty concentrating, with no history of elevated mood. Which diagnosis is most consistent with this presentation, and why? Guidance: Major Depressive Disorder — symptoms match the depressive episode criteria with no reported manic/hypomanic history.

6. A patient describes a 5-day period of needing only 3 hours of sleep, feeling unusually confident, and talking rapidly, followed weeks later by a depressive episode. Identify the likely diagnosis. Guidance: Bipolar II Disorder — the "up" period matches hypomania (4+ days, no marked impairment described) combined with a major depressive episode.

Analysis

7. Compare how a clinician would distinguish Cyclothymic Disorder from Bipolar II Disorder using DSM-5 criteria. Guidance: Cyclothymia involves numerous periods of hypomanic and depressive symptoms that never meet full criteria for either a hypomanic or major depressive episode, over 2+ years; Bipolar II requires at least one full hypomanic episode and one full major depressive episode.

8. Evaluate why combining psychotherapy and medication is generally considered more effective than either alone for mood disorders. Guidance: Medication addresses biological/neurochemical symptoms relatively quickly; psychotherapy builds coping skills, addresses maintaining thought patterns, and reduces relapse risk — combined treatment addresses both mechanism and long-term resilience.

FAQ

Is it normal to feel down sometimes, or does that mean I have a mood disorder? Everyone experiences low moods occasionally, and this is not the same as a mood disorder. A diagnosis requires a specific symptom cluster lasting at least two weeks (for depression) and causing significant impairment in daily functioning. Occasional sadness that resolves on its own is a normal part of life, not a disorder.

Can someone have both depression and an anxiety disorder at the same time? Yes, this is extremely common — anxiety and mood disorders frequently co-occur (comorbidity). In fact, many people with MDD also meet criteria for an anxiety disorder, and treatment plans often need to address both simultaneously.

Why is lithium still used for bipolar disorder when newer medications exist? Lithium has decades of evidence supporting its effectiveness as a mood stabilizer and is uniquely associated with reduced suicide risk in bipolar patients. Despite requiring regular blood monitoring due to its narrow therapeutic range, it remains a first-line treatment because of this strong evidence base.

Does postpartum depression differ from regular Major Depressive Disorder? Postpartum depression is diagnosed using the same MDD criteria, but with the "peripartum onset" specifier, indicating onset during pregnancy or within four weeks after childbirth. Hormonal shifts, sleep deprivation, and major life adjustment contribute to its onset, and it requires prompt attention given its impact on both parent and infant.

Can mood disorders be cured completely? Many mood disorders are episodic and treatable, with many people achieving full remission and returning to their previous level of functioning. However, both MDD and bipolar disorder can be recurrent, so ongoing management — including recognising early warning signs and maintaining treatment — is often part of long-term care rather than a one-time "cure."

Quick Revision

• Mood disorders split into depressive disorders (persistently low mood) and bipolar disorders (cycling between depression and mania/hypomania)
• MDD requires 5+ symptoms over 2 weeks, including depressed mood or anhedonia, with functional impairment
• Mania: 1+ week, marked impairment, possible psychotic features; Hypomania: 4+ days, no marked impairment
• Bipolar I needs a full manic episode; Bipolar II needs hypomania plus a major depressive episode, never full mania
• Cyclothymic Disorder is chronic subthreshold mood cycling lasting 2+ years
• Common diagnostic tools: BDI, PHQ-9, HAM-D (depression); YMRS (mania)
• SSRIs/SNRIs are first-line for MDD; mood stabilizers like lithium are first-line for bipolar disorder
• Giving antidepressants alone to a bipolar patient risks triggering mania/hypomania
• CBT and interpersonal therapy are leading evidence-based psychotherapies for mood disorders
• Sleep regulation is especially critical in preventing bipolar relapse
• Mood disorders are often recurrent, so long-term management matters as much as acute treatment

Related Topics

Prerequisites Introduction to Psychological Disorders

Related Topics Anxiety Disorders, Psychotic Disorders, Psychological Assessment, Treatment and Therapy

Next Topics Anxiety Disorders, Psychotic Disorders