Insomnia: why falling or staying asleep gets hard, and what the science says

What it actually is

Insomnia is persistent difficulty initiating or maintaining sleep, or achieving restorative sleep, despite having adequate opportunity and circumstances to sleep. The Diagnostic and Statistical Manual of Mental Disorders (DSM-5, American Psychiatric Association, 2013) defines chronic insomnia disorder as these difficulties occurring at least three nights a week for a minimum of three months, along with significant distress or daytime impairment. Below that time threshold, it's called acute or short-term insomnia, often tied to an identifiable trigger such as a stressful event, travel, or a schedule change. The International Classification of Sleep Disorders (ICSD-3, American Academy of Sleep Medicine, 2014) sets out equivalent criteria and identifies insomnia as the most common sleep disorder in the general population.

Why it takes hold and persists: the 3P model and hyperarousal

Psychologist Arthur Spielman proposed the so-called 3P model in 1987 (Psychiatric Clinics of North America), still a reference framework in sleep medicine: predisposing factors (a biological or personality tendency toward light sleep or worry), precipitating factors (a specific event that triggers insomnia, such as a loss or a stressful period), and perpetuating factors (the habits a person adopts to compensate — staying in bed awake trying harder to sleep, or taking long naps — which end up maintaining the problem long after the original trigger has faded). In parallel, Michael Perlis and other sleep researchers describe chronic insomnia as a state of hyperarousal: the nervous system of people with insomnia shows objective signs of heightened physiological and cognitive activation — higher metabolic rate, more high-frequency brain activity — both day and night, making it hard to 'switch off' even when real tiredness is present.

The link to anxiety and depression — real, but not a verdict

Numerous epidemiological studies document a well-established bidirectional association between insomnia and conditions like anxiety and depression: having one raises the risk of developing the other, and not always in the same order. In some cases insomnia precedes and predicts a later depressive episode; in others, it's a symptom appearing within an already-present anxiety picture. But this statistical association doesn't mean automatic or universal causation: many people with chronic insomnia have no diagnosable mental health condition at all, and their difficulty sleeping stems from other factors — irregular schedules, habits, another medical condition, or simply a learned hyperarousal pattern, as described in the 3P model. A psychological diagnosis should not be assumed just from sleeping poorly.

Signs it might be happening

The clinical signs that typically point toward insomnia include: regularly taking more than 30 minutes to fall asleep, frequent nighttime awakenings with difficulty getting back to sleep, waking up much earlier than intended and being unable to resume sleep, and a sense of unrefreshing sleep even after spending enough time in bed. For this to count as insomnia in the clinical sense, these difficulties need to come with a real daytime impact: fatigue, trouble concentrating or remembering things, irritability, sleepiness, or reduced performance at work or school. Sleeping badly on one particular night, or less than usual after travel or an upsetting event, is not the same as having insomnia as a disorder.

What to do — and what not to expect from this article

This article is educational, not a diagnosis or a treatment. The treatment with the strongest scientific backing for chronic insomnia is Cognitive Behavioral Therapy for Insomnia (CBT-I): a 2016 clinical practice guideline from the American College of Physicians recommends it as first-line treatment, ahead of hypnotic medication, because its effects hold up better long-term and it avoids the dependence or tolerance risks associated with some sleeping pills. CBT-I combines techniques like stimulus control, time-in-bed restriction, and restructuring thoughts about sleep, and is typically delivered by a psychologist or a clinician trained in sleep medicine. It's worth seeing a doctor if insomnia persists beyond a few weeks, clearly affects your daily life, or you suspect it may relate to another condition (sleep apnea, chronic pain, a mood disorder). Ensuenia does not diagnose or treat insomnia; this page summarizes published scientific literature so you know what to ask, and who to ask.

A related tool: your sleep debt

Insomnia and sleep debt are distinct but connected concepts: sleep debt is the accumulated gap between the sleep your body needs and the sleep you're actually getting, whatever the cause. If you've had several nights of sleeping less than you need — whether from insomnia or anything else — that buildup can intensify daytime fatigue and, in some cases, feed back into difficulty sleeping well. You can run a rough estimate with our sleep debt calculator, available on Ensuenia; it's an informational tool, not a diagnostic one, but it can help put a number on what you already suspect and decide whether it's worth talking to a professional.

Frequently asked questions

Sources

• American Psychiatric Association, Diagnostic and Statistical Manual of Mental Disorders, 5th edition (DSM-5) (2013) — Define los criterios clínicos del trastorno de insomnio crónico: dificultad para dormir ≥3 noches/semana durante ≥3 meses con malestar o deterioro diurno.
• American Academy of Sleep Medicine, International Classification of Sleep Disorders, 3rd edition (ICSD-3) (2014) — Establece criterios equivalentes para el insomnio y lo identifica como el trastorno del sueño más frecuente en la población general.
• Arthur J. Spielman, A behavioral perspective on insomnia treatment (1987) — Psychiatric Clinics of North America; formula el modelo de las 3P (predisponentes, precipitantes, perpetuantes) para explicar cómo se instala y se mantiene el insomnio crónico.
• Michael L. Perlis et al., Neurobiologic mechanisms in chronic insomnia (2009) — Sleep Medicine Clinics 4(4):549-558; describe el modelo de hiperactivación (hyperarousal) fisiológica y cognitiva en el insomnio crónico.
• American College of Physicians, Management of Chronic Insomnia Disorder in Adults: A Clinical Practice Guideline (2016) — Annals of Internal Medicine; recomienda la Terapia Cognitivo-Conductual para el Insomnio (TCC-I) como tratamiento de primera línea, por delante de la medicación hipnótica.