Serotonin (5-HT) dysregulation may be associated with both suicidal behaviors (Mann et al.1999; Mann, 2002) and substance abuse (e.g. Javors et al. 2005; Morgan, 2000). Alterations in 5-HT function (LeMarquand et al. 1994a, 1994b; Mann, 1998; Owens and Nemeroff, 1994) and other systems involved in cell signaling and signal modulation (Pandey et al. 1997, 2002, 2004) have been linked to suicide and suicidal behavior. Among adults, Malone and colleagues (1996) showed that alterations in central 5-HT function were especially pronounced in suicide attempters who were younger than age 30. In post-mortem studies of adolescents, Pandey and colleagues (1997, 2002, 2004) showed that, compared to deceased controls, adolescent suicide completers had increased 5-HT2A receptor mRNA and protein expression in the prefrontal cortex and hippocampus. Higher levels of 5-HT2A receptors may be one of the neurobiological abnormalities associated with adolescent suicidal behavior. Other biological factors related to completed suicide are decreased protein kinase A and C, down-regulated CREB, and increased activity of brain-derived neurotrophic factor (BDNF) in the prefrontal cortex and hippocampus (Pandey et al. 2004). These latter findings suggest that both the serotonin system, and cell signaling and signal modulation are linked to suicidal behaviors.
