What is the medical diagnosis for symptoms of fatigue, insomnia, and generalized weakness?

Medical Diagnosis for Fatigue, Insomnia, and Generalized Weakness

The triad of fatigue, insomnia, and generalized weakness requires systematic evaluation to distinguish between primary sleep disorders, psychiatric conditions, medical comorbidities, and medication effects—with chronic insomnia disorder being the most common unifying diagnosis when these symptoms persist for ≥3 months.

Primary Diagnostic Considerations

Chronic Insomnia Disorder

This is the most likely diagnosis when symptoms include difficulty initiating or maintaining sleep occurring ≥3 nights per week for ≥3 months, accompanied by daytime fatigue and functional impairment 1. The American Academy of Sleep Medicine emphasizes that insomnia diagnosis requires both nighttime sleep complaints AND associated daytime dysfunction 1.

Key diagnostic features include:

• Fatigue (not sleepiness) is the predominant daytime complaint in chronic insomnia patients, whereas true sleepiness suggests alternative sleep disorders like sleep apnea 1
• Generalized weakness or limb heaviness is a recognized component of insomnia-related daytime impairment 1
• Cognitive difficulties, irritability, and reduced motivation commonly accompany the physical symptoms 1

Psychiatric Disorders

Depression and anxiety disorders account for approximately 18.5% of persistent fatigue cases and frequently present with this symptom triad 2. The American Academy of Sleep Medicine guidelines note that mood disturbances (irritability, mild depression, anxiety) are common among insomnia patients 1. However, criterion D requires that symptoms not be primarily attributable to major depression, somatization disorder, or delirium 1.

Medical Conditions

While organic causes are relatively uncommon, specific conditions warrant consideration:

• Anemia and other organic causes account for only 4.3% of persistent fatigue cases 2
• Sleep-related breathing disorders (obstructive sleep apnea) can present with fatigue, insomnia, and weakness 1
• Previously undiagnosed cancer is rare, representing only 0.6% of fatigue presentations 2
• Endocrine disorders, cardiovascular disease, and neurological conditions should be evaluated 3

Diagnostic Workup Algorithm

Step 1: Comprehensive Sleep and Symptom History

Obtain detailed information about 1, 4, 3:

• Sleep-wake patterns: bedtime, sleep onset latency (time to fall asleep), number and duration of nighttime awakenings, final wake time, total sleep time
• Symptom chronicity: duration ≥3 months and frequency ≥3 nights per week establishes chronicity 1
• Daytime consequences: distinguish between fatigue (low energy, physical tiredness) versus sleepiness (tendency to fall asleep) 1
• Pre-sleep conditions: activities, environment, cognitive arousal
• Napping patterns: frequency, duration, voluntary versus involuntary 1

Step 2: Screen for Comorbid Conditions

Complete systematic review of 1, 3:

• Psychiatric history: depression, anxiety, bipolar disorder, PTSD using validated screening tools
• Medical conditions: cardiovascular, pulmonary, gastrointestinal, pain syndromes, endocrine disorders
• Medication review: SSRIs, beta-blockers, stimulants, decongestants, corticosteroids, diuretics all can cause or worsen insomnia 1, 3
• Substance use: caffeine intake (timing and quantity), alcohol, nicotine, recreational drugs 1, 3

Step 3: Required Assessment Tools

Minimum required documentation 1, 4, 3:

• Two-week sleep diary/log: documenting bedtime, wake times, sleep latency, awakenings, total sleep time, naps 1, 4
• Epworth Sleepiness Scale: to identify excessive sleepiness suggesting alternative sleep disorders 1, 3
• General medical/psychiatric questionnaire: to identify comorbid conditions 1

Actigraphy for ≥7 days is strongly indicated when circadian rhythm disorders are suspected or to objectively confirm sleep-wake patterns 4, 3.

Step 4: Laboratory Testing (Selective)

Laboratory studies affect management in only 5% of patients with fatigue 5. Testing should be guided by history and physical examination findings, not performed routinely 2. Consider:

• Complete blood count (to evaluate for anemia)
• Thyroid function tests
• Basic metabolic panel
• Additional testing only if specific clinical indicators present 5, 2

Step 5: Polysomnography Indications

Polysomnography is NOT indicated for routine insomnia evaluation 1. It is indicated only when there is reasonable clinical suspicion of 1:

• Sleep-related breathing disorders (sleep apnea)
• Periodic limb movement disorder
• Other primary sleep disorders

Critical Diagnostic Pitfalls to Avoid

Do not confuse fatigue with sleepiness 1, 4. Patients with chronic insomnia typically report fatigue, low energy, and weariness rather than actual tendency to fall asleep. Significant sleepiness should prompt evaluation for sleep apnea or other primary sleep disorders 1.

Avoid excessive laboratory testing 5, 2. If initial laboratory results are normal, repeat testing is generally not indicated unless new symptoms emerge 5. An exclusively somatic focus leads to overdiagnosis 2.

Do not overlook medication-induced insomnia 1, 3. SSRIs, venlafaxine, stimulants, decongestants, beta-blockers, and many other commonly prescribed medications can cause or exacerbate insomnia 1.

Recognize that multiple conditions may coexist 4. Insomnia frequently occurs alongside depression, anxiety, chronic pain, or medical conditions—these are comorbid conditions, not necessarily causal 1.

Specific Diagnostic Criteria

For Chronic Insomnia Disorder (DSM-5/ICSD-3)

Requires ALL of the following 1:

• Dissatisfaction with sleep quantity or quality
• Difficulty initiating or maintaining sleep, or early-morning awakening
• Symptoms present ≥3 nights per week
• Symptoms persist ≥3 months
• Clinically significant distress or functional impairment
• Adequate opportunity for sleep
• Not better explained by another sleep disorder, medical condition, or substance

For Cancer-Related Fatigue (if applicable)

Requires ≥6 symptoms present daily for ≥2 weeks, including 1:

• Significant fatigue, diminished energy (criterion A1)
• Generalized weakness or limb heaviness (criterion A2)
• Insomnia or hypersomnia (criterion A5)
• Plus clinically significant functional impairment (criterion B)
• Evidence linking symptoms to cancer or cancer therapy (criterion C)

Treatment Implications Based on Diagnosis

Cognitive Behavioral Therapy for Insomnia (CBT-I) is the first-line treatment for chronic insomnia disorder and should be initiated immediately upon diagnosis 1, 3, 6. CBT-I has demonstrated efficacy not only for insomnia but also for improving fatigue, with insomnia improvement accounting for 45.3% of fatigue reduction 7.

If CBT-I alone is insufficient after 2-4 weeks, pharmacological therapy may be added using shared decision-making 1, 6. First-line pharmacological options include short-intermediate acting benzodiazepine receptor agonists or ramelteon 6.

For patients with comorbid depression, SSRIs may improve energy levels, though they can paradoxically worsen insomnia in some patients 1, 5.