Although both subtyping approaches had significant moderating effects, inspection of the figures showing weekly drinking measures suggests that the moderator effects were greater for the age-of-onset than for the cluster-derived subtypes. Although Roache et al. (2008) also found that age of onset was a better moderator of treatment response than the cluster-derived subtypes, in that study the differences seen between the two subtyping approaches were more evident than those seen here. This may reflect differences in the effects of the medications used, since sertraline has direct effects on serotonin reuptake via the serotonin transporter with secondary effects on postsynaptic receptors (McRae and Brady 2001), while the primary effects of ondansetron are on serotonin-3 receptors (Wilde and Markham 1996), with other postsynaptic receptors being affected as well (McNulty 2007).
