Figure 1.

Cocaine KMSK scores in the whole cohort, by genotype. KMSK scores are on an ordinal integer scale, where “0” denotes no lifetime exposure (never used drug; see Methods), and greater scores denote increasing exposure (maximum score=16). Cocaine KMSK scores measure exposure at the point in a volunteer’s life when use was at its heaviest. A cocaine KMSK value ≥9 has optimal concurrent validity with a cocaine dependence diagnosis (DSM-IV criteria). Individual data points are shown in the scatter plot. The width of the data shown for each score is proportional to the number of subjects with that score. The red line shows the median score. The data were analyzed with a Mann–Whitney test (* denotes p=0.047).