What are the symptoms, diagnostic tests, and treatments for anxiety disorders, depression, Attention Deficit Hyperactivity Disorder (ADHD), substance use disorders, and bronchiolitis, and how do they differ from one another?

Distinguishing Anxiety Disorders, Depression, ADHD, Substance Use Disorders, and Bronchiolitis

These five conditions differ fundamentally in their core symptom patterns, diagnostic approaches, and treatment strategies, with anxiety disorders characterized by excessive worry and fear responses, depression by persistent low mood and anhedonia, ADHD by developmentally inappropriate inattention and hyperactivity, substance use disorders by compulsive substance-seeking behavior, and bronchiolitis by acute respiratory symptoms in infants—each requiring distinct evaluation and management protocols.

Core Symptom Patterns

Anxiety Disorders

• Primary symptoms: Developmentally inappropriate, excessive worry or distress with 8 subcategories including separation anxiety, social anxiety, and generalized anxiety disorder 1
• Key features: Symptoms must be time-consuming (>1 hour daily) and cause substantial distress or functional impairment 1
• Distinguishing characteristics: Intrusive thoughts are ego-dystonic (unwanted) and irrational, unlike the reality-based worries of depression 1
• Somatic manifestations: Headaches, gastrointestinal symptoms, and physical complaints are common presentations 1

Depression (Major Depressive Disorder)

• Primary symptoms: Persistent low mood, anhedonia (loss of interest/pleasure), and ruminations about real-life concerns 1
• Key differentiator: Worries are typically about actual life circumstances rather than irrational fears, and compulsions are absent 1
• Associated features: Sleep disturbance, appetite changes, fatigue, and concentration difficulties 2
• Critical warning: Screen for bipolar disorder before initiating antidepressant treatment, as treating a depressive episode with antidepressants alone may precipitate manic episodes in at-risk patients 2

ADHD

• Core symptom domains: Inattention (easily distracted, failing to follow through on tasks) and/or hyperactivity-impulsivity (restlessness, interrupting others) 1, 3
• Diagnostic requirement: Symptoms must be present in more than one major setting (home, school, work) and cause functional impairment 1
• Age considerations: Symptoms must have onset before age 12, though diagnosis can occur later 1
• Persistence: 14.6% of U.S. adults meet DSM-5 criteria, indicating frequent continuation into adulthood 3

Substance Use Disorders

• Defining feature: Compulsive substance-seeking behavior with an ego-syntonic, gratifying component in the short term 1
• ADHD association: Hyperactive-impulsive symptoms show stronger correlation with substance use than inattentive symptoms 4
• Risk factors: Untreated ADHD significantly increases risk for substance use disorders, with odds ratios of 4.6 compared to those without ADHD 5
• Critical screening: All adolescents with ADHD require assessment for substance use given elevated risk 1, 6

Bronchiolitis

• Note: This respiratory condition in infants is unrelated to the psychiatric conditions above and was not addressed in the provided evidence base.

Diagnostic Testing Approaches

Anxiety Disorders

• Screening tools: Parent- and Self-Rated Level 1 Cross-Cutting Symptom Measures (freely available from APA) for systematic identification 1
• Structured interviews: Anxiety Disorders Interview Schedule for DSM-5 (ADIS-5) for both adults and children 1
• Collateral information: Input from family members, teachers, and other clinicians adds diagnostic depth 1
• Medical workup: Laboratory testing (glucose, thyroid function) only if signs suggest medical conditions like hyperthyroidism, caffeinism, or cardiac arrhythmias 1

Depression

• Bipolar screening: Detailed psychiatric history including family history of suicide, bipolar disorder, and depression before starting antidepressants 2
• Assessment measures: Structured Clinical Interview for DSM-5 (SCID-5) for diagnostic confirmation 1
• Monitoring requirements: Close observation for clinical worsening, suicidality, and unusual behavior changes, especially during initial treatment months 2

ADHD

• Standardized rating scales: Essential for documenting symptoms across multiple settings 1
• Multi-informant approach: Reports from parents/guardians, teachers, school personnel, and mental health clinicians 1
• Mandatory comorbidity screening: Anxiety, depression, oppositional defiant disorder, conduct disorders, substance use, learning disabilities, language disorders, autism spectrum disorders, tics, and sleep apnea 1, 7, 6
• Alternative cause exclusion: Rule out medical conditions, medication effects, and other psychiatric disorders before confirming ADHD 1

Substance Use Disorders

• Adolescent assessment: Minimum screening for substance use symptoms and signs in all adolescents with ADHD 1
• Monitoring tools: Controlled substance agreements and prescription drug monitoring programs when prescribing stimulants 3
• Collateral information: Urine drug screening and information from multiple sources 3

Treatment Algorithms

Anxiety Disorders

First-line treatment:

• Cognitive-behavioral therapy (CBT): Evidence-based psychotherapy targeting anxiety-specific symptoms 1
• Selective serotonin reuptake inhibitors (SSRIs): When psychotherapy insufficient or unavailable 1

Critical warning: Monitor for activation symptoms (agitation, panic attacks, insomnia, irritability, hostility, impulsivity) when starting SSRIs, as these may represent precursors to suicidal ideation 2

Depression

Treatment initiation:

• Antidepressants: Fluoxetine and other SSRIs are first-line pharmacotherapy 2
• Black box warning: All patients require monitoring for suicidality, especially during initial months and dose changes 2
• Symptom monitoring: Watch for anxiety, agitation, panic attacks, insomnia, irritability, hostility, aggressiveness, impulsivity, akathisia, hypomania, and mania 2

Discontinuation: Taper medication rather than abrupt cessation to avoid withdrawal symptoms 2

ADHD

Age 4-5 years (preschool):

• First-line: Parent training in behavior management (PTBM) and/or behavioral classroom interventions 1, 6
• Second-line: Methylphenidate only if behavioral interventions fail and moderate-to-severe functional impairment persists 1

Age 6-12 years (elementary/middle school):

• First-line: FDA-approved ADHD medications (stimulants: methylphenidate or amphetamine) PLUS parent training and behavioral classroom interventions 1, 6
• Educational supports: Individualized Education Plan (IEP) or 504 plan as necessary component 1

Age 12-18 years (adolescents):

• First-line: FDA-approved ADHD medications with adolescent's assent 1
• Adjunctive: Evidence-based behavioral interventions when available 1
• Critical screening: Assess for substance use, anxiety, depression, and learning disabilities as these affect treatment sequencing 1, 6

ADHD with comorbid anxiety:

• Primary ADHD: Start with stimulants, which often improve both ADHD and anxiety symptoms 8
• Persistent anxiety: Add anxiety-specific treatment (CBT or SSRI) if stimulants don't alleviate anxiety 8
• Alternative: Atomoxetine shows efficacy for both ADHD and anxiety symptoms 8
• Optimal approach: Combination of medication and CBT superior to medication alone 8

ADHD with possible bipolar disorder:

• Diagnostic clarification first: Determine true bipolar disorder versus ADHD with severe mood dysregulation before treatment 9
• Mood dysregulation: Start with stimulant trial, as stimulants reduce both ADHD symptoms and aggressive behaviors in majority of children 9
• True bipolar disorder: Stabilize mood first with lithium (FDA-approved age ≥12) or mood stabilizers, then cautiously add stimulants for residual ADHD symptoms 9

Substance Use Disorders

In context of ADHD:

• Monitoring: Controlled substance agreements and prescription drug monitoring programs when prescribing stimulants 3
• Treatment approach: Address substance use disorder before or concurrently with ADHD treatment 1
• Medication selection: Consider atomoxetine, viloxazine, or bupropion as non-stimulant alternatives if stimulant diversion risk is high 3

Critical Comorbidity Patterns

High Overlap Conditions

• ADHD-Anxiety: 65-89% of adults with ADHD have comorbid psychiatric disorders, with anxiety disorders showing odds ratio of 5.0 10, 5
• ADHD-Depression: Odds ratio of 4.5 for major depressive disorder in adults with ADHD versus without 5
• ADHD-Substance Use: Odds ratio of 4.6, with hyperactive-impulsive symptoms more strongly associated than inattentive symptoms 4, 5
• Anxiety-Depression: Commonly co-occur and require separate treatment plans 1

Treatment Implications

• Each comorbid disorder requires separate treatment plan and influences anxiety disorder treatment selection 1
• Comorbidities heighten distress, worsen functional impairment, and may worsen treatment outcomes 1
• Presence of comorbid conditions alters ADHD treatment approach, requiring chronic care model management 1, 7

Common Diagnostic Pitfalls

Misdiagnosis Risks

• Anxiety masquerading as ADHD: Medical conditions (hyperthyroidism, caffeinism, cardiac arrhythmias) can mimic anxiety symptoms 1
• Depression versus anxiety: Both involve worry, but depression focuses on real-life concerns while anxiety involves irrational fears 1
• ADHD versus anxiety: Concentration difficulties occur in both; distinguish by presence of hyperactivity-impulsivity and multi-setting impairment 1
• Bipolar versus depression: Treating unrecognized bipolar disorder with antidepressants alone may precipitate mania 2

Assessment Errors

• Single-source information: ADHD diagnosis requires multi-informant data from multiple settings 1
• Incomplete comorbidity screening: Missing anxiety, depression, learning disabilities, or substance use leads to inadequate treatment 1, 6
• Language barriers: Lack of appropriate interpreter support associated with misdiagnosis and adverse outcomes 1

Treatment Mistakes

• Premature discontinuation: ADHD treatments frequently not maintained over time, leading to increased risk for adverse outcomes including early death, suicide, lower educational achievement, and incarceration 6
• Monotherapy for complex cases: Combined medication and behavioral therapy superior to either alone for anxiety and ADHD 8
• Ignoring educational needs: School-based interventions and IEP/504 plans are necessary components of ADHD treatment 1