 Some variations in 5-HT neurotransmission may thus contribute to a risk of AD (alcohol dependence), especially the forms of AD associated with a high level of impulsivity.As the extracellular concentration of 5-HT is regulated by the activity of the 5-HT transporter (5-HTT), the gene SLC6A4 encoding this protein represents an important potential candidate gene for AD risk.Using a meta-analysis approach, Feinn et al.