Table 1. Demographic, clinical, and endophenotypic characteristics of the autistic sample.

	N	Mean/median	Range
Age in years (mean±SEM):	N=306	9.18±0.33	2–33
Median VABS scores:	N=137
Communication		69.0	19–128
Daily living skills		67.0	14–170
Socialization		66.0	25–140
Motor skills		80.0	25–128
Composite		60.0	19–137
Head circumference: (median percentile±IQR/2)	N=265	82.5±23.75	2.5–98.5
Serotonin blood levels: (mean ng/ml±SEM)	N=158	329.5±20.9	31.0–987.1
Urinary oligopeptiduria: (mean μm2±SEM)	N=231	346.2±16.5	57–1213
	N		Percent (%)
Gender:
Male	269		87.9
Female	37		12.1
M/F ratio	7.3:1
Family type:
Simplex	281		95.9
Multiplex	12		4.1
DSM-IV diagnosis:
Autistic disorder	207		67.6
Asperger syndrome	27		8.8
PDD – NOS	72		23.6
IQ (N=71):
>70	18		25.4
<70	53		74.6

Abbreviations: IQR/2, semi-interquartilic range; PDD – NOS, pervasive developmental disorder – not otherwise specified.