The Three Ps of Insomnia: Why Treatment Targets the Perpetuating Factors
Insomnia is one of the clearest cases in clinical psychology where the thing that caused a disorder and the thing maintaining it are not the same, and where effective treatment deliberately ignores the cause.
Arthur Spielman's model, set out in the late 1980s and still the standard teaching frame, divides the picture into three. Predisposing factors are what someone brings with them: a tendency toward hyperarousal, an anxious temperament, family history, being female, being older. Precipitating factors are the events that start it — a bereavement, a divorce, illness, a period of shift work, a stretch of acute stress. Perpetuating factors are the behaviours and beliefs adopted in response, which keep the insomnia running after the precipitant has resolved.
The clinically interesting part is that the third category does most of the work. Patients routinely present with insomnia that has outlasted its trigger by years. They can often name the week it began and cannot understand why it never stopped.
What maintains it
The perpetuating factors belong to a class that will be familiar from anxiety disorders and chronic pain: responses that reduce distress in the short term and sustain the problem over the long term. Safety behaviours in panic, activity avoidance in persistent pain, and sleep-effort behaviours here share a structure — each is a reasonable-looking attempt at control that removes the very conditions under which the problem would resolve.
The clearest instance is time in bed. Someone sleeping badly extends the sleep window, going to bed earlier or lying in later, on the entirely sensible assumption that more opportunity produces more sleep. It produces the opposite. The same quantity of sleep is distributed across a longer period, which fragments it and lowers sleep efficiency, and the surplus wakefulness accumulates in the one place where it does most damage.
Because the bed is a cue. Through repeated pairing with wakefulness, frustration and rumination it stops predicting sleep and begins predicting arousal. The frequently reported pattern of falling asleep readily in an armchair and becoming alert on transferring to bed is its clearest clinical expression. Richard Bootzin built stimulus control therapy directly on this observation in the early 1970s, and it remains the component with the most transparent theoretical rationale.
What makes perpetuating factors counter-intuitive is that they are sensible. Nobody adopts them out of ignorance. They are what a reasonable person does when they are not sleeping.
The components
Cognitive behavioural therapy for insomnia is a multicomponent package. The standard formulation has five elements, each targeting a different perpetuating mechanism.
Sleep restriction compresses time in bed toward the amount of sleep actually obtained. A patient in bed nine hours and sleeping six has the window cut toward six. This works on Process S in Borbély's two-process model: concentrating homeostatic sleep pressure shortens sleep onset and consolidates the sleep that follows, which raises sleep efficiency — the ratio of time asleep to time in bed. The window is then widened in increments as efficiency climbs, typically at a threshold in the high eighties. It is the most demanding of the five to follow, because the first stretch increases daytime sleepiness before sleep consolidates.
Stimulus control breaks the learned association between the bed and wakefulness. Bootzin's instructions are procedural: go to bed only when sleepy, get out of bed if awake for a prolonged period and return only when sleepy again, use the bed for sleep and sex alone, rise at the same time every day regardless of how the night went, and avoid daytime napping. The instruction to get out of bed rather than wait it out is counter-intuitive to nearly every patient and is usually the one they resist.
Cognitive therapy addresses the beliefs generating pre-sleep arousal: catastrophic predictions about the consequences of a poor night, unrealistic expectations about normal sleep continuity, and the attribution of every daytime difficulty to sleep. Charles Morin's work on dysfunctional beliefs and attitudes about sleep is the reference point, and the scale he developed is still widely used to measure them. The anxiety about not sleeping is itself a perpetuating factor, which makes the fear partly self-fulfilling.
Relaxation training targets the somatic and cognitive arousal that precedes sleep — progressive muscle relaxation, diaphragmatic breathing, autogenic training, imagery. It is the component that works on state rather than on scheduling or conditioning, which is why it sits alongside the others rather than substituting for them. Mindfulness-based approaches to insomnia are related but developed as a separate treatment lineage rather than as a CBT-I component.
Sleep hygiene education covers the environmental and lifestyle factors: caffeine and alcohol timing, light, temperature, exercise. It is routinely included and routinely misunderstood. For most patients it is the only part they have encountered before presenting, which creates the impression that they have already tried the treatment and it did not work. In fact they have tried the element that is least effective on its own, and none of the four that carry the effect.
Why it's recommended ahead of medication
The American College of Physicians recommends CBT-I as the first-line treatment for chronic insomnia in adults, ahead of medication. The mechanistic reasoning is consistent with the model above: hypnotics act on the symptom and leave the perpetuating factors untouched, so the problem tends to return on discontinuation, whereas a behavioural intervention alters the conditions producing it.
Delivery
CBT-I is delivered by trained clinicians, through structured self-help materials, and increasingly in digital form. The evidence base rests largely on the therapist-delivered version; the other formats exist because the supply of trained CBT-I clinicians is far smaller than the prevalence of the disorder. Among the digital options, Rest applies cognitive behavioural therapy for insomnia (CBT-I) principles in a conversational format.
Across all three, adherence is the variable that predicts outcome, and the components patients most want to drop are the ones carrying the effect.