Data from a study illustrates the interaction between 5-HTTLPR gene variants and childhood maltreatment on the likelihood of chronic adult depression. Among individuals with no history of childhood maltreatment before age 9, the rates of chronic depression were relatively low and similar across all gene types: approximately 23% for the Long-Long version, 19% for the Long-Short, and 20% for the Short-Short. However, for those who did experience childhood maltreatment, the risk of chronic depression dramatically increased for carriers of the short allele. Their rates were approximately 53% for the Long-Short version and 71% for the Short-Short version, while the rate for the Long-Long version remained low at about 22%, similar to the non-maltreated group.