Differential Diagnosis

Common Diagnoses

  • Anxiety from Excess Psychological Stress (Work, Relationships, Finance)
  • Clinical Depression
  • Chronic Alcohol Excess
  • Poor Sleep Hygiene: Hyperstimulation (e.g. Caffeine, Nicotine, Drugs, Exciting Television Films) and Daytime Naps
  • Pain of Chronic Physical Illness (e.g. Osteoarthritis)

Occasional Diagnoses

  • Menopausal Flushes and Sweats
  • Nocturia
  • External Problems (e.g. Snoring Partner, Children who Disturb Parental Sleep)
  • Biorhythm Disruption: Jet Lag and Shift Work
  • Respiratory Problems: Asthma, Chronic Obstructive Pulmonary Disease (COPD), Left Ventricular Failure (LVF) Commonest
  • Benzodiazepine Withdrawal
  • Other Medical Problem, e.g. Restless Legs Syndrome or Gord

Rare Diagnoses

  • Malnutrition and Low Body Weight
  • Post-Traumatic Stress Disorder
  • Parasomnias: Nightmares, Night Terrors and Sleepwalking
  • Hyperthyroidism
  • Mania
  • Sleep Apnoea (Usually Presents as ‘Tired all the Time’ [TATT]; only 30% Aware of Waking)

Ready Reckoner

Key distinguishing features of the most common diagnoses

StressDepressionAlcoholPoor Sleep HygienePain
Slow to go offYesPossiblePossibleYesPossible
Early Morning WakingPossibleYesNoNoPossible
Low MoodPossibleYesPossibleNoPossible
Physical Illness TooNoNoPossibleNoYes
Weight LossPossiblePossibleNoNoPossible

Possible Investigations


Possible:FBC, LFT, TFT.

Small Print:Investigation of primary symptom leading to insomnia (see Possible investigations).

  • FBC (MCV), LFT and γGT may show evidence of chronic alcohol misuse.
  • TSH will differentiate non-organic anxiety state from thyrotoxicosis.
  • NOTE: Pain, nocturia, respiratory problems and sleep apnoea may require investigating in their own right.

Top Tips

  • Uncover any underlying physical problem such as pain or nocturia and manage as appropriate – it is pointless adopting a ‘sleep hygiene’ approach when the problem is primarily physical.
  • Don’t forget the role of alcohol; this is often an underlying or contributory cause, paradoxically taken by the patient to relieve the insomnia.
  • If the diagnosis seems likely to be tension or poor sleep hygiene, establish the patient’s agenda early. Patients who simply want sleeping pills are unlikely to listen to well-intentioned advice until this issue has been discussed and resolved.
  • Explain to elderly patients that sleep requirements fall with increasing age and that daytime naps are to be discouraged.

Red Flags

  • Shift workers are significantly at risk of developing clinical depression. Be sure to assess carefully for this pathology in the insomniac shift worker.
  • Beware of young male temporary residents presenting ‘urgently’ with insomnia. They may well be drug addicts trying to obtain a prescription for benzodiazepines.
  • Bone or joint pain waking an elderly patient at night is highly significant. In the patient with known arthritis, joint replacement may be indicated; in others, it may indicate serious bony pathology such as secondaries.
  • Take the problem seriously even if the cause seems trivial or obvious (e.g. a patient’s snoring) – insomnia can be extremely debilitating, and by the time patients attend, they may be desperate for help.
  • Anxiety and severe weight loss with sweating and tachycardia suggests hyperthyroidism. Be sure to check TSH before deciding this is non-organic.

Published: 2nd August 2022 Updated: 10th April 2024

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