Drowsiness is also referred to as sleepiness, somnolence and hypersomnia, and is a strong desire to sleep during waking or daytime hours. Drowsiness is related to many different psychological, medical and lifestyle causes, and can be reduced by changes in habits and treating any underlying health issues.
In some people, depression, which is also referred to as clinical depression or major depression, may cause drowsiness and a strong desire to sleep. People who experience grief may also have an extended period of drowsiness while coping with their feelings. Drowsiness that is accompanied by a loss of desire for previously enjoyed activities and persistent feelings of sadness may indicate depression.
Changes in hormone levels may cause drowsiness, especially in women. Changes in the levels of estrogen and progesterone as well as other hormones may occur during premenstrual syndrome, in pregnancy and after childbirth. An underactive thyroid, or hypothyroidism, can also be a cause of drowsiness.
Many types of illnesses can cause feelings of drowsiness and fatigue during the course of the disease. Respiratory disorders such as emphysema and chronic obstructive pulmonary disorder may cause chronic drowsiness. Other long-term illnesses, including diabetes, heart disease and cancer, can also cause drowsiness.
Some types of medications may cause drowsiness as a side effect, and this can interfere with normal functioning and activities. Antihistamines such as Benadryl that are used to treat allergies are a common cause of drowsiness. Other medications that can cause drowsiness include antidepressants and pain relievers.
Personal habits or lifestyle routines may be a cause of drowsiness when there is no obvious medical reason for the condition. Staying up too late and then not getting enough sleep is a common cause of drowsiness. Working different shifts at a job, working a lot of hours and engaging in strenuous physical activity can also result in drowsiness.
Sleep disorders that cause difficulty with falling asleep, staying asleep or getting into the deep stages of sleep can cause drowsiness during the day. Insomnia, the inability to fall asleep or stay asleep for several days or longer, can occur in children and adults. Other sleep disorders that can cause drowsiness include narcolepsy, sleep apnea and restless legs syndrome.