More research, using objective measures, is needed to determine the association between napping and sleep disturbances. There are many underlying causes of a patient s sleep disturbances. A common cause of many sleep disorders is a medical condition. Psychiatric illness, such as depression and anxiety, could also lead to sleep disorders. Many types of alcohol and drugs may lead to sleep disorders.
Alcohol leads to drowsiness, frequent awakenings, loss of REM sleep, and increased sleep apnea.
Restless legs syndrome is a disorder which is characterized by tingling pain and pressure in legs, leading to the urge to move the legs. The presence of restless legs syndrome causes an increased latency of the onset of sleep. The studies reviewed did not use standard selection criteria and used a variety of recording techniques, so the results are not easily compared. Another problem with many of the research studies was that they did not consider the night to night variations in sleep apnea. Many studies revealed that there was no causal relationship between sleep apnea syndrome and cardiovascular disease or impairment of cognitive function.