Even in this fast-paced and hectic world, sleep is one of those things that are considered indispensable. Regardless of how much stress is placed on someone, a person's body and mind simply will not allow one to go for an extended period without some sleep. There are numerous ways to keep a person awake despite the overwhelming desire to go to sleep, such as caffeine and work-related stress and anxiety. The toll that sleep deprivation and insomnia have on the body is well-documented, but there is less concrete evidence on the effects on mental health. It is generally assumed that the mind does not fully shut down during sleep, but that does not mean it does not require a period of rest. There are several potential side effects of insomnia upon one's mental health, some of which can aggravate the problem itself.
Among the most well-documented side effects of a lack of sleep is instability of emotions. People who frequently lack sleep tend to be moody and irritable. In some cases, their emotions seem to be on hair-triggers, shifting from “normal” to “angry” with the slightest comment. There has yet to be any form of concrete information on why this is the cause, but it is a well-documented problem related to insomnia. It is theorized that sleep somehow replenishes certain chemical receptors related to emotions within the brain, such that a lack of sleep disrupts the normal production of these chemicals. It is currently unclear whether being asleep cuts off production or increases them, or if it affects these compounds in some other way. There are other theories as to why insomnia affects emotions, but those also lack concrete studies to back up their assumptions.
One of the more infamous side effects of insomnia is depression, though it is arguable whether one is really a product of the other. In the same way that emotions are affected by a lack of sleep, one's overall mood can also be affected by prolonged insomnia. Since depression is closely tied to one's emotional state, the disruption caused by a lack of sleep can be enough to push a person into clinical depression. However, there is some argument as to whether or not insomnia is truly a factor for depression. There are some that believe that while there is a connection, it is more viable to assume that depression leads to a lack of sleep, rather than the other way around. It should be noted that, despite the ramifications on mental health, neither theory has been put under serious academic scrutiny.
Some have also attributed some anxiety disorders to insomnia. There is some question as to whether or not this actually counts, however. While there is clear evidence that connects the two problems, most are inclined to believe anxiety disorders cause insomnia, rather than the reverse. However, there is some data showing people developing minor anxiety disorders during a period where they lack adequate sleep. As with the above, further study is required due to the lack of any concrete statistical data to back up the theories and observations.