Mood Disorders in Adolescence

Definition and Core Concepts

Mood disorders represent a spectrum of interrelated psychiatric conditions characterized by a fundamental deficit in emotional self-regulation.
They are broadly divided into depressive disorders (featuring dysphoric or "low" mood) and bipolar disorders (featuring euphoric or "high" mood alongside depressive episodes).
These disorders are highly prevalent in the pediatric population, ranking as the most common psychiatric illnesses following attention-deficit/hyperactivity disorder (ADHD) and anxiety disorders.
Adolescents typically present with distinct clinical features compared to younger children; whereas young children may present predominantly with somatic complaints and irritability, adolescents are more likely to exhibit overt disturbances in energy, activity levels, sleep, and appetite.

Depressive Disorders

A Major Depressive Episode is defined by a distinct period of at least two weeks featuring a depressed or irritable mood and/or a loss of interest or pleasure (anhedonia) in almost all activities, present most of the day, nearly every day.
Diagnosis requires the presence of at least five symptoms that represent a clear change from previous functioning, causing significant psychosocial or academic impairment.

Depressive Disorder Subtype	Diagnostic Criteria and Nuances
Major Depressive Disorder (MDD)	Requires $\geq$ 2 weeks of depressed/irritable mood or anhedonia, plus a constellation of neurovegetative and cognitive symptoms. In youth, failure to make expected weight gains is considered alongside weight loss.
Persistent Depressive Disorder (Dysthymia)	Characterized by a depressed or irritable mood for more days than not, lasting for at least 1 year in children and adolescents. Symptoms must not be absent for more than 2 months at a time.
Disruptive Mood Dysregulation Disorder (DMDD)	Features severe, recurrent temper outbursts (verbal or physical) occurring $\geq$ 3 times per week for $\geq$ 12 months. The baseline mood between outbursts is persistently irritable. Diagnosis cannot be made before age 6 or after age 18, and onset must be before age 10.

The SIGECAPS Mnemonic for Depressive Symptoms

The SIGECAPS mnemonic is highly useful in clinical interviews to systematically identify the fundamental, neurovegetative, and neurocognitive symptoms of depression.

Mnemonic Letter	Symptom Domain	Clinical Manifestations
S	Sleep	Insomnia or hypersomnia nearly every day.
I	Interest	Anhedonia; markedly diminished interest or pleasure in activities.
G	Guilt	Feelings of worthlessness or excessive, inappropriate guilt.
E	Energy	Fatigue or pervasive loss of energy nearly every day.
C	Concentration	Diminished ability to think, concentrate, or make decisions.
A	Appetite	Significant weight loss, weight gain, or failure to meet expected weight milestones.
P	Psychomotor	Observable psychomotor agitation or retardation.
S	Suicidality	Recurrent thoughts of death, suicidal ideation, specific plans, or attempts.

Bipolar Disorders

Bipolar disorders are characterized by periods of abnormal mood elevation (mania or hypomania) interspersed with or followed by depressive episodes.
A manic episode involves a distinct period of at least one week with an abnormally elevated, expansive, or irritable mood, accompanied by persistently increased goal-directed activity or energy.
Classic manic symptoms in adolescents include inflated self-esteem or grandiosity, a decreased need for sleep (feeling rested after only a few hours), pressured speech, flight of ideas, extreme distractibility, and reckless involvement in activities with a high potential for painful consequences (e.g., substance abuse, sexual indiscretions).

Bipolar Disorder Subtype	Diagnostic Distinctions
Bipolar I Disorder	Requires the presence of at least one full manic episode ( $\geq$ 7 days, or any duration if hospitalization is necessary). Psychotic features (delusions, hallucinations) may be present.
Bipolar II Disorder	Requires at least one hypomanic episode ( $\geq$ 4 consecutive days) AND at least one major depressive episode. There must be no history of a full manic episode. The hypomanic episode causes observable changes but is not severe enough to cause marked functional impairment or require hospitalization.
Cyclothymic Disorder	Characterized by at least 1 year (in adolescents) of numerous periods featuring hypomanic and depressive symptoms that never meet the full criteria for a hypomanic or major depressive episode.

Etiology and Risk Factors

Genetic Pathways: Mood disorders exhibit significant heritability. Monozygotic twin studies demonstrate concordance rates of 40% to 65% for depressive disorders. Bipolar disorder demonstrates even higher heritability, estimated between 60% and 90%, and shares familial co-aggregation with schizophrenia.
Biologic Factors: Implicated biologic vulnerabilities include hypothalamic-pituitary-adrenal (HPA) axis abnormalities, serotonergic dysfunction, and structural variations in the amygdala and anterior paralimbic cortices.
Environmental Stressors: For depression, highly predictive environmental factors include physical or sexual abuse, neglect, social isolation, bullying, academic failure, and severe family disharmony. For bipolar disorder, early onset is frequently triggered by an interaction between genetic vulnerability and environmental factors such as negative parenting styles and childhood trauma.

Differential Diagnosis and Comorbidities

The diagnosis of a mood disorder requires the rigorous exclusion of other medical and psychiatric etiologies that mimic dysphoria, irritability, or mania.

Category	Specific Differential Diagnoses
Psychiatric Conditions	Attention-Deficit/Hyperactivity Disorder (ADHD), Oppositional Defiant Disorder (ODD), Anxiety Disorders, Substance Use Disorders, Adjustment Disorder, Eating Disorders, and Schizophrenia Spectrum Disorders.
Medical/Systemic Illnesses	Hypothyroidism, hyperthyroidism, anemia, autoimmune encephalitis, chronic fatigue syndrome, systemic infections, and central nervous system tumors.
Substance/Medication-Induced	Illicit drugs (cocaine, methamphetamines), alcohol, corticosteroids, beta-blockers, oral contraceptives, and isotretinoin.

Evaluation and Screening

The clinical interview must prioritize assessing the onset, duration, severity, and context of symptoms, as well as the degree of functional impairment in academic and social domains.
Direct and private assessment of the adolescent for suicidal ideation, suicidal intent, and self-injurious behavior is absolutely mandatory.
Standardized screening tools validated for adolescents include the Patient Health Questionnaire-9 (PHQ-9) for ages 12 and above, the Beck Depression Inventory for Youth, the Mood and Feelings Questionnaire (MFQ), and the Mood Disorder Questionnaire for bipolar screening.

Management Principles

Psychotherapy

Psychotherapy is highly efficacious and should be considered the first-line treatment for mild to moderate depression and an essential adjunct for severe depression and bipolar disorders.
Cognitive-Behavioral Therapy (CBT): Focuses on identifying and correcting cognitive distortions and teaching behavioral activation, problem-solving, and emotional regulation. Response rates are comparable to pharmacotherapy in the long term.
Interpersonal Psychotherapy (IPT): Specifically targets the resolution of interpersonal difficulties and conflicts, enhancing social communication skills, and expanding social support networks.
Family-Focused Therapy: Strongly indicated for bipolar disorders to reduce family conflict, enhance communication, and decrease affective arousal, which lowers relapse rates.

Pharmacotherapy for Depressive Disorders

Selective Serotonin Reuptake Inhibitors (SSRIs) are the only class of medications approved by the US Food and Drug Administration (FDA) for pediatric depression.
Fluoxetine is approved for children 8 years and older; Escitalopram is approved for adolescents 12 years and older.
Black Box Warning: All SSRIs carry an FDA warning regarding an increased risk of suicidal thinking and behavior in patients under 25 years of age. Rigorous monitoring is mandated (weekly for the first 4 weeks, then biweekly for weeks 4 through 8).
Common side effects include gastrointestinal upset, headaches, insomnia, and akathisia. Behavioral activation (motor restlessness, disinhibition) may occur and necessitate a dosage reduction.
If no improvement is observed after an adequate 8-week trial at the maximum tolerated dose, cross-tapering to a different SSRI (e.g., Sertraline, Citalopram) is indicated.

Pharmacotherapy for Bipolar Disorders

Antidepressant Contraindication: Antidepressants must never be used as monotherapy in confirmed Bipolar I disorder due to the high risk of precipitating an iatrogenic manic switch.
Atypical Antipsychotics: Considered the first-line pharmacotherapy for acute mania in adolescents. Aripiprazole, Risperidone, Olanzapine, and Quetiapine are highly efficacious but carry significant risks for weight gain, metabolic syndrome, and extrapyramidal symptoms.
Mood Stabilizers: Lithium is FDA-approved for acute mania and maintenance in patients 12 years and older. It requires strict monitoring of serum trough levels (therapeutic range 0.8–1.2 mEq/L), thyroid function, and renal function. Valproic acid may be used as an alternative or adjunct, requiring monitoring of liver function tests and complete blood counts.