Symptoms
If you lose a little sleep, then you're just tired. If you miss an entire night's sleep then you can expect to have reduced attention span, trouble with your short term memory such as forgetting what your doing. Most obviously, longer term lack of sleep can lead to tremors in limb extremities and twitching of muscles. Taking a more physiological point of view, chronic partial lack of sleep can lead to reduced capacity in processing and storing carbohydrates and to regulate hormone secretion. A study at University of Chicago Medical centre showed that subjects ability to process and produce insulin was severely reduced (30% down), similar to the response of patient with early stages of diabetes. The study also saw other symptoms similar to those of old age. They concluded that sleep loss could both hasten the onset and increase the severity of age related diseases.
In another study, a 17 year old volunteer went without sleep for 264 hours, he was the best performer in a group of subjects. He was also one of the youngest in the study (there's the age thing again). This particular study looked at things like sleep patterns and behaviour among other things. They noted that sleep deprivation can lead to irritability, blurred vision, slurring of speech, memory lapse and confusion concerning the subject's own identity, generally, fatigue and loss of concentration. After 5 to 10 days of of continuous sleep deprivation, brief hallucinations occured along with episodes of unusual behaviour. The short term effects were such the the subject might have done himself an injury had he not been observed constantly. Subjects might also lapse into "microsleep".
In tasks that involve responding to a stimulus, subjects tended to do worse than when performing "self-paced" tasks. Subjects often suffered errors of omission associated with microsleep. Any lapses in concentration after mild loss of sleep can be compensated for with extra effort.
Longterm effects
In rats, long term sleep deprivation has been known to cause debilitation and death. In humans, experimentation has not pointed to any adverse effects on intellect or physical wellbeing. This might be due to the fact that sleep loss studies have been limited in length and since proving such effects could be "unpleasant" morally. Any psychosis that appeared after recovery of the 17 year old subject seem be in stages of development anyway.
What can cause sleep deprivation?
Excess consumption of caffeine, usually coffee. Other stimulants like speed, redbull, certain prescription drugs. Illness such as insomnia or hyposomnia. Teething babies is another good one.
Cures?
Sleep!
If you have anything to add or something is inaccurate, /msg me.
Sources of info.
www.medhelp.org/perl6/neuro/archive/14759.html
www.people.cornell.edu/pages/msd10/sleep.html
www.britannica.com/bcom/eb/article/printable/9/0,5722,117529,00.html