Low serotonin levels lead to a variety of psychiatric disorders that, while they might seem unrelated on the surface, all result from an overriding sense of discomfort and anxiety. Patients with low serotonin tend to feel uncomfortable, because serotonin is a neurotransmitter responsible for feelings of happiness, relaxation and well-being. Whether low serotonin is the result of a brain chemical imbalance that an individual was born with or is secondary to another medical issue, symptoms can be quite severe.
Obsessive-Compulsive Disorder
The American Academy of Family Physicians explains that one of the disorders categorized as a serotonin deficiency-related illness is obsessive-compulsive disorder. In this psychiatric condition, patients feel obsessed with certain issues, like cleanliness or order, and are therefore compelled to engage in what they perceive as related behaviors, including rigorous and repetitive cleaning or hand washing. Researchers have determined that low levels of serotonin in the brain are responsible for many cases of obsessive-compulsive disorder, and physicians prescribe pharmaceuticals that help increase brain levels of serotonin. These drugs help reduce or relieve symptoms entirely, allowing individuals with obsessive-compulsive disorder to live normal lives.
Addiction
One of the most recent illnesses to come to light as a result of low serotonin levels in the brain is addiction. Typically, addiction has been considered to be the result of low dopamine levels in the brain. Dopamine is another neurotransmitter and works closely with serotonin in many regards. Wellesley College reports that research using mice with congenital serotonin deficiencies has revealed that such mice are born essentially addicted to cocaine. Scientists can conjecture by extension that the mice in question would also be likely to display addictions to other strongly addictive substances, such as nicotine or heroin. It appears that low serotonin levels can predispose individuals toward addictive behaviors.
Depression
The classic illness associated with low serotonin levels is depression. Bryn Mawr College explains that serotonin acts as an important "feel-good" neurotransmitter, sending signals that an individual is relaxed and happy. In the absence of serotonin, patients feel sad and unwell and may even experience fear, anxiety and physical discomfort. Drugs to treat depression help the brain increase levels of serotonin, either by preventing breakdown of serotonin that's released from the nerves or by keeping serotonin in the space between the nerves for a longer period of time, which enhances "happiness" signals.
