Insomnia is classified into three categories - transient, intermittent and chronic. Though the duration and intensity vary, the symptoms are the same for all of them.

Insomnia by itself is not a disease, but a symptom of an underlying disease or life style problem. There are many causes of sleepless nights, including physical and psychological disorders and behavior patterns. So, looking for the symptoms of insomnia alone is not sufficient and must form a part of a wider investigation.

When a person does not fall asleep for a long time after going to bed (around 45 minutes) and tosses and turns, in spite of counting sheep, it is a symptom of insomnia. Pain - physical or mental - is the most obvious reason and the most common. The reason for failing to sleep could be that the mind is racing or hyperactive and aroused due to stress, anxiety or some traumatic experience.

The second symptom is waking up frequently and finding it difficult to go back to sleep. This could be due to various sleep disorders, hormonal imbalances as with menopausal women, respiratory problems and life style related causes.

The third symptom is waking up too early. This is a symptom of some underlying malady like obstructive sleep apnea or other respiratory disorders.

The fourth symptom of insomnia is poor quality of sleep. A complete night's sleep consists of four deepening stages and rapid eye movement (REM) sleep. Stages 3 and 4 are very important ones for rejuvenating the body and the mind and if this stage is not reached the quality of sleep seems very poor.

The most important aspect of studying these symptoms and their causes is to relate them in the context of the patient's perception of the quantity and quality of sleep.