states of mind - anxiety, depression, worry, anger, grief, anticipating a difficult event

change - moving house/city, starting university

environment - noise, discomfort, time zone change

pain - one of the commonest causes

medical conditions - heart, breathing, stomach, digestive, high blood pressure, arthritis, anorexia.

recreational drugs - including nicotine, caffeine, heroin, cocaine, amphetamines, LSD, cannabis

sleeping pills and tranquillisers - can actually cause sleep disturbance

other prescription drugs - including some contraceptives, diuretics, slimming pills, beta-blockers, stimulants.

Sleep Onset Insomnia (Delayed Sleep Phase Syndrome): A disorder in which the major sleep episode is delayed in relation to the desired clock time that results in symptoms of sleep onset insomnia or difficulty in awakening at the desired time.

Idiopathic Insomnia: A lifelong inability to obtain adequate sleep that is presumably due to an abnormality of the neurological control of the sleep-wake system. The insomnia is long-standing, commonly beginning in early childhood, sometimes since birth.

Psychophysiological Insomnia: A disorder of somatized tension (conversion of anxiety into physical symptoms) and learned sleep-preventing association that results in a complaint of insomnia and associated decreased functioning during wakefulness.

Childhood Insomnia (Limit-Setting Sleep Disorder): Primarily a childhood disorder that is characterized by the inadequate enforcement of bedtimes by a caretaker with resultant stalling or refusal to go to bed at the appropriate time.
Another kind of insomnia that generally affects children is called Sleep-Onset Association Disorder. This disorder occurs when sleep onset is impaired by the absence of a certain object or set of circumstances, such as being held, rocked or nursed; television watching, radio listening, etc.

Food Allergy Insomnia: A disorder of initiating and maintaining sleep due to an allergic response to food allergens. It is typically associated with the introduction of a new food or drink, i.e., cow's milk.

Enviornmental Insomnia (Enviornmental Sleep Disorder): A sleep disturbance due to a disturbing enviornmental factor that causes a complaint of either insomnia or excessive sleepiness.

Transient Insomnia (Adjustment Sleep Disorder): Represents sleep disturbance temporally related to acute stress, conflict or enviornmental change causing emotional agitation.

Periodic Insomnia (Non 24-Hour Sleep-Wake Syndrome): Consists of a chronic (lasting a long time) steady pattern consisting of 1-2 hour daily delays in sleep onset and wake times in an individual living in society.

Altitude Insomnia: An acute (short and sharp course, not chronic) insomnia usually accompanied by headaches, loss of appetite, and fatigue, that occurs following ascent to high altitudes. (Unless you are a mountain climber or a mountain goat, this kind of insomnia won't apply)

Hypnotic-Dependency Insomnia ( Hypnotic- Dependent Sleep Disorder ): Characterized by insomnia or excessive sleepiness that is associated with tolerance to or withdrawal from hypnotic medications.

Stimulant-Dependent Sleep Disorder: Charcterized by a reduction of sleepiness or suppression of sleep by central stimulants, and resultant alterations in wakefulness following drug abstinence.

Alcohol-Dependent Insomnia (Alcohol-Dependent Sleep Disorder): Characterized by the assisted initiation of sleep onset by the sustained ingestion of alcohol that is used for its hypnotic effect.

Toxin-Induced Sleep Disorder: Characterized by either insomnia or excessive sleepiness produced by poisoning with heavy metals or organic toxins.