In broad terms, insomnia refers to difficulty experienced in falling asleep or maintaining restoring/refreshing sleep. While many people regard the state of insomnia as a sleep disorder, a number of them disagree and insist on insomnia being regarded as a symptom rather than a distinct disorder. Whether disorder or symptom, different kinds of insomnia have been recognized and are described here.

Sleep Onset Insomnia

This state of insomnia is also called Delayed Sleep Phase Syndrome because the patient tends to delay the major sleep episode according to the desired time of dropping off. This delay causes sleeplessness and difficulty in getting up at the desired time.

Psycho-Physiological Insomnia

In this case anxiety (psychological problem) creates physical symptoms and prevents sleep. One characteristic of this state of insomnia is that the patient feels physical problems in/on the sleeping place (bed) and this hinders the sleep.

Idiopathic Insomnia

In some cases the nervous system becomes incapable of controlling the sleeping and waking mechanism of the body. The result is a lifelong failure to get proper sleep. This state of insomnia is called idiopathic insomnia and it usually starts in early childhood.

Childhood Insomnia

Insomnia in children is of two types. In the first case, the sleep disturbance results when a child refuses to go to bed or delays sleep due to inadequate enforcement of bedtimes by the guardian. This is referred to as Limit-Setting Sleep Disorder. The second condition, called, Sleep-Onset Association Disorder, occurs when children cannot go to sleep due to absence of their ideal conditions (presence of a toy, a favorite blanket, the state of being rocked etc.).

Altitude Insomnia

Altitude Insomnia is an acute version of insomnia, short-lived but intense, accompanied by symptoms of headache, fatigue, and loss of appetite, all occurring when you move to high altitudes.

Food Allergy Insomnia

Insomnia that results as an allergic response to certain foods is called Food Allergy Insomnia. Usually it occurs in response to some new foods that have not previously been part of the person's diet.

Toxin-Induced Sleep Disorder

Poisoning with toxins like heavy metals or certain organic compounds can cause sleeplessness. Such a state of insomnia is regarded as toxin-induced insomnia.

Environmental Insomnia

This sleep difficulty is caused by the presence of certain environmental factors in the surrounding e.g. noise, smell, smoke etc.

Stimulant-Dependent Sleep Disorder

Insomnia may result from using substances (drugs for example) that stimulate the nervous system. The person becomes addicted to their use and fails to get sleep when abstinence from the drug is practiced.