Which neurotransmitter is decreased in individuals suffering from mood disorders?

Individuals suffering from mood disorders often exhibit decreased levels of serotonin, which is a neurotransmitter that plays a critical role in regulating mood, emotion, and behavior. Serotonin influences a number of psychological functions, including feelings of well-being and happiness. Low levels of serotonin are commonly associated with mood disorders such as depression and anxiety, contributing to symptoms like sadness, irritability, and a general lack of interest in life.

Research has consistently indicated that increasing serotonin levels through various treatments, such as antidepressant medications known as selective serotonin reuptake inhibitors (SSRIs), can help alleviate symptoms of mood disorders. Therefore, the relationship between serotonin and mood regulation is a well-established concept in psychology and psychiatry, making it the correct answer to the question.