Sleep Disorders Every Therapist Should Know: A Clinical Overview with ICD-10 Codes
Sleep problems land in therapist offices constantly. For many clients, disrupted sleep is center to what’s keeping them stuck. The exhaustion, the mood dysregulation, the cognitive fog, the anxiety spiral that starts at 2am. They are often a clinical target in their own right.
But here’s the thing: not all sleep problems are insomnia. And for therapists who haven’t had specific sleep medicine training, distinguishing between sleep disorders (knowing what to treat, what to refer, and what questions to ask) can feel murky.
Lets get into an overview of the major sleep problems that covers how each condition presents, its diagnostic classification, relevant ICD-10 codes, and what mental health clinicians need to know. The International Classification of Sleep Disorders, Third Edition identifies over 80 different sleep disorders, but I’m only going to cover ones that are most likely going to show up in your caseload.
A quick note on coding: as mental health therapists, we bill using F codes under ICD-10-CM (the behavioral and mental health chapter). The G codes listed throughout this post are used by physicians and sleep medicine specialists. You won’t be billing with G codes but knowing it exists and what it means makes you a better collaborator with the medical providers on your client’s team.
Insomnia Disorder
What it is
Insomnia is the most common sleep disorder and one therapists are most likely to encounter. It’s characterized by dissatisfaction with sleep quantity or quality, with difficulty falling asleep, staying asleep, or waking up too early, occurring at least three nights per week for at least three months, with real daytime impairment.
A 2025 meta-analysis estimating global insomnia prevalence found pooled prevalence of 12.4% of clinical interview and DSM criteria. Also, a 2024 narrative review noted that about 1/3 of adults experience initiation or maintenance difficulty at least weekly.
DSM-5 Criteria Highlights:
Difficulty initiating sleep, maintaining sleep, or early morning awakening
Occurs great than three nights per week for over three months
Causes clinically significant distress or functional impairment
Not better explained by another sleep disorder, substance or medical condition
Note: DSM-5 removed the primary/secondary insomnia distinction. Insomnia disorder is now diagnosed independently, even when comorbid conditions are present.
ICD-10 Codes
F51.01 = Primary Insomnia
F51.09 = Other insomnia not due to substance or known physiological condition
G47.00 = Insomnia, unspecified
G47.01 = Insomnia due to medical condition
G47.09 = Other insomnia
Clinical Note for Therapists
Insomnia is highly comorbid with anxiety and depression. And treating it directly with CBT-I has been shown to improve those conditions, too. If a client presents with chronic insomnia, it warrants clinical attention. For a deep dive on, check out my post on what CBT-I actually is.
Sleep Apnea (Sleep-Disordered Breathing)
What it is
Sleep apnea is a serious sleep disorder in which breathing repeatedly stops and starts during sleep. The most common form called obstructive sleep apnea (OSA) occurs when the muscles at the back of the throat relax and block the airway. Central sleep apnea involves the brain failing to send appropriate signals to the breathing muscles.
OSA is significantly underdiagnosed. Classic presentations include loud snoring, witnessed breathing pauses, and excessive daytime sleepiness but many people (especially women) present atypically with insomnia, fatigue, mood disturbance, and morning headaches, making it easy to miss in a therapy context.
ICD-10 Codes
G47.30 = Sleep apnea, unspecified
G47.31 = Primary central apnea
G47.33 = Obstructive sleep apnea (adult)
G47.37 - Central sleep apnea in conditions classified elsewhere
Clinical Note for Therapists
If a client presents with unexplained daytime fatigue, mood issues, and reports snoring or being told they stop breathing in sleep then a medical evaluation for OSA should happen before or alongside therapy for insomnia. CBT-I is appropriate alongside treated OSA, but should not be the only intervention if sleep apnea is suspected.
Narcolepsy
What it is
Narcolepsy is a chronic neurological disorder involving dysregulation of the sleep-wake cycle, characterized by excessive daytime sleepiness and uncontrollable sleep attacks. There are two types. Type 1 (formerly narcolepsy with cataplexy) is associated with low hypocretin (orexin) levels and is thought to involve an autoimmune process. Type 2 (formerly without cataplexy) is less well characterized.
Narcolepsy is rare. A 2023 US population study found Type 1 affects about 12.6 per 100,000 people and Type 2 about 25.1 per 100,000. Despite this, diagnosis is frequently delayed, the average time from symptom onset to diagnosis has been reported at up to 14 years.
Classic Symptoms:
• Excessive daytime sleepiness (EDS) — the hallmark symptom; irresistible sleep attacks
• Cataplexy — sudden muscle weakness triggered by strong emotion (laughter, excitement, surprise); pathognomonic for Type 1
• Sleep paralysis — temporary inability to move at sleep onset or awakening
• Hypnagogic/hypnopompic hallucinations — vivid, often frightening hallucinations at sleep onset or awakening
• Disrupted nighttime sleep — fragmented, poor quality nocturnal sleep despite excessive daytime sleepiness
ICD-10 Codes
G47.411 = Narcolepsy with cataplexy (type 1)
G47.419 = Narcolepsy without cataplexy (type 2)
G47.421 = Narcolepsy in conditions classified elsewhere, with cataplexy
G47.429 = Narcolepsy in conditions classified elsewhere, without cataplexy
Clinical Note for Therapists
Narcolepsy frequently gets misidentified as depression, ADHD, or laziness, especially in adolescents, where onset is common. If a client describes irresistible daytime sleep attacks, episodes of muscle weakness triggered by emotion, or recurring sleep paralysis, narcolepsy warrants consideration and medical referral. Therapy can support coping and quality of life, but the primary treatment is medical.
Restless Leg Syndrome (RLS or Willis-Ekbom Disease)
What it is
Restless Legs Syndrome (RLS), also called Willis-Ekbom Disease, is a neurological sensorimotor disorder characterized by an irresistible urge to move the legs, typically accompanied by uncomfortable sensations such as crawling, tingling, burning, aching. Symptoms worsen during rest and at night, and are temporarily relieved by movement.
A 2024 systematic review and modelling analysis estimated global RLS prevalence at 7.12% among adults aged 20–79 affecting approximately 356 million people worldwide. Despite its prevalence, RLS is frequently unrecognized or misdiagnosed, with many patients going undiagnosed for 10–20 years.
Diagnostic criteria (IRLSSG)
Urge to move the legs, usually accompanied by uncomfortable sensations
Urge begins or worsens during rest or inactivity
Partially or totally relieved by movement
Worse in the evening or at night than during the day
Not explained by another condition or behavior
ICD-10 Codes
G25.81 = Restless Leg Syndrome
Clinical Note for Therapists
RLS significantly disrupts sleep initiation and quality, and is strongly associated with anxiety and depression. Clients may describe it in ways that sound like anxiety (restlessness, inability to settle at night) or even somatic symptoms. If a client reports uncomfortable leg sensations at bedtime that compel them to move, ask specifically about the pattern like is it worse at night, worse at rest, and temporarily relieved by movement. Medical referral is appropriate; secondary RLS has known associations with iron deficiency, pregnancy, and kidney disease.
Circadian Rhythm Sleep-Wake Disorders
What they are
Circadian rhythm sleep-wake disorders occur when a person's internal sleep-wake clock is misaligned with their environment or desired schedule. They're not just about being a "night owl" but they represent a genuine mismatch between the body's circadian timing and the demands of daily life.
The most commonly seen in clinical practice:
Delayed Sleep Phase Disorder (DSPD): Sleep onset and wake times are shifted significantly later. Common in adolescents and young adults. The person can't fall asleep until 2–4am and struggles to wake for morning obligations.
Advanced Sleep Phase Disorder (ASPD): The opposite of sleep and wake are shifted much earlier. More common in older adults.
Shift Work Sleep Disorder: Caused by work schedules that conflict with natural circadian rhythms. Highly relevant for healthcare workers, first responders, and anyone working overnight shifts.
Jet Lag Disorder: Temporary misalignment following rapid travel across time zones.
Irregular Sleep-Wake Rhythm: No clear circadian rhythm; sleep is fragmented across 24 hours. Associated with neurodegenerative conditions.
ICD-10 Codes
G47.21 = Circadian rhythm sleep disorder, delayed sleep phase type
G47.22 = Circadian rhythm sleep disorder, advanced sleep phase type
G47.23 = Circadian rhythm sleep disorder, irregular sleep wake type
G47.24 = Circadian rhythm sleep disorder, free running type
G47.25 = Circadian rhythm sleep disorder, jet lag type
G47.26 = Circadian rhythm sleep disorder, shirt work type
G47.27 = Circadian rhythm sleep disorder in condition classified elsewhere
Clinical Note for Therapists
Circadian rhythm disorders are frequently misidentified as insomnia or laziness. A client who describes being completely unable to fall asleep before 3am but sleeps fine when they finally do may have DSPD rather than insomnia disorder, and the CBT-I protocol would need to be adapted accordingly. Ask about preferred sleep and wake times, and whether the client can sleep fine on a shifted schedule (like on vacation or weekends with no obligations).
Parasomnias
What they are
Parasomnias are abnormal behaviors or experiences that occur during sleep, at sleep onset, or during arousals from sleep. They're divided into NREM-related and REM-related categories.
NREM-related parasomnias include:
Sleepwalking (Somnambulism): Complex behaviors performed during deep sleep with no recall upon waking
Sleep terrors: Sudden arousal with intense fear, screaming, and autonomic activation such as a person appears awake but is not, and typically has no memory of the episode
Confusional arousals: Partial awakening with disorientation and altered behavior
Sleep-related eating disorder: Eating during partial arousals from sleep
REM-related parasomnias include:
REM Sleep Behavior Disorder (RBD): Acting out vivid, often violent dreams during REM sleep, the normal muscle paralysis of REM is absent. Clinically significant because RBD is a known precursor to Parkinson's disease and other neurodegenerative conditions
Nightmare disorder: Recurrent, distressing nightmares causing significant functional impairment which is distinct from the occasional bad dream and highly comorbid with PTSD, anxiety, and trauma
Sleep paralysis: Temporary inability to move at sleep onset or awakening, sometimes accompanied by hallucinations
ICD-10 Codes
F51.3 = Sleepwalking (somnambulism)
F51.4 = Sleep terrors
F51.5 = Nightmare disorder
G47.52 = REM sleep behavioral disorder
G47.51 = Confusional arousals
Clinical Note for Therapists
Nightmare disorder is the parasomnia most commonly encountered in therapy , especially with trauma-focused work. Image Rehearsal Therapy (IRT) is an evidence-based treatment specifically for nightmares and is often integrated into PTSD treatment. RBD warrants prompt medical referral given its association with neurodegeneration. Sleepwalking and sleep terrors in adults (rather than children, where they're more common) also merit evaluation.
Hypersomnia/Idiopathic Hypersomnia
What it is
Hypersomnia refers to excessive daytime sleepiness despite adequate or prolonged nighttime sleep. Idiopathic hypersomnia is characterized by severe daytime sleepiness without a clear cause, like the person sleeps long hours and still cannot feel fully awake. Unlike narcolepsy, cataplexy is absent and sleep attacks are less sudden.
Hypersomnia can also be secondary caused by depression, medication, other sleep disorders, or medical conditions. Clinicians should differentiate primary hypersomnia from secondary causes before drawing conclusions.
ICD-10 Codes
G47.11 = Idiopathic hypersomnia with long sleep time
G47.12 = Idiopathic hypersomnia without long sleep time
F51.11 = Primary hypersomnia
G47.10 = Hypersomnia, unspecified
When to Refer: A Quick Therapist Guide
Not everything sleep related requires a referral or is a diagnosis but some things do. Here’s a quick decision guide:
Refer for medical evaluation if: client reports snoring, has witnessed apneas, excessive daytime sleepiness despite adequate sleep, symptoms of RLS, cataplexy, recurrent sleep paralysis, hallucinations, or acting out dreams physically.
Assess and potentially treat with therapy if: client presents with insomnia disorder, nightmare disorder, circadian rhythm disruption related to schedule or habits or sleep anxiety, particularly if trained in CBT-I or behavioral sleep interventions.
Consult or co-treat if: sleep disorder is comorbid with a psychiatric condition you’re treating. Insomnia alongside anxiety or depression often warrants treating both simultaneously.
Sleep is Clinical
Sleep disorders don't stay in their lane. They intersect with mood, cognition, trauma, chronic illness, and quality of life in ways that make them impossible to ignore in a therapy context. The more fluent therapists become in recognizing and addressing sleep disorders or knowing when to refer, the better the outcomes for the clients sitting across from them.
If you're a therapist interested in building your sleep competency, especially around CBT-I, that's exactly what my consulting work is designed for. And if you're a client reading this and recognizing your own pattern in any of the descriptions above then that's a good starting place for a conversation.
Ready to Go Deeper?
I offer CBT-I informed therapy for clients in Illinois and Texas and CBT-I consulting for therapists who want to integrate sleep interventions into their clinical practice. Contact me today.
