We also characterized heterogeneity using the pairwise average number of shared symptoms. Those with exactly two symptoms shared, on average, only 0.70 symptoms (s.d.=0.62). The average number of shared symptoms almost doubled to 1.36 (s.d. = 0.72) among those with exactly three symptoms, and rose to 2.14 (s.d. =0.79) and 2.98 (s.d. =0.84) among those with exactly four and five symptoms, respectively. Cases with two or more symptoms shared an average of 1.58 symptoms (s.d. = 1.19), but this number increased to 2.52 (s.d. = 1.37) in the 3 + group, 3.51 (s.d. = 1.48) in the 4 + group, and 4.51 (s.d. = 1.55) in the 5 + group. These results indicate that increasing the threshold for diagnosis with the DSM-5 draft criteria would substantially reduce the degree of heterogeneity among diagnosed cases.
