We surveyed the incoming class of 2014 at Princeton University about their intended academic major, familial incidence of neuropsychiatric disorders, and demographic variables. We received 1077 responses from 1313 students, a response rate of 82%. 527 respondents indicated a technical major (natural sciences, engineering, or mathematics), 394 indicated non-technical majors (245 in social sciences, 149 in humanities), and 156 students were undecided. A follow-up survey determined the mean number of siblings per student to be 1.5.
We began by looking for a previously reported relation between ASDs and technical interests 
. Twenty-four freshmen (2.2%, 1 in 45) reported having a sibling with an ASD. This included 16 of 527 (3.0%, 1 in 33) aspiring technical majors compared with 4 of 394 (1.0%, 1 in 99) nontechnical students, for an odds ratio of 3.05 (χ2
0.037). Thus the incidence of ASDs amongst siblings of technical majors was significantly higher than that of non-technical majors and roughly twice (after correction based on number of siblings) the US average of 1 in 160 
We calculated relations between the reported familial incidence of surveyed disorders and other neurological conditions and two groupings became apparent (). One consisted of bipolar disorder, major depressive disorder, substance abuse, post-traumatic stress disorder (PTSD), and attention deficit hyperactivity disorder (ADHD). The other included Alzheimer's disease, memory loss, and stroke. On the basis of their correlations, we grouped these conditions with a hierarchical agglomerative algorithm (). Several of these relations reflect known comorbidities and familial aggregations 
Familial co-occurrence of neuropsychiatric disorders.
We tested for correlations between individual disorders and intended major in a hypothesis-free manner. Significant associations were seen for bipolar disorder (p
0.027), major depression (p
), and substance abuse (p
; all p-values adjusted for multiple comparisons) (). Each was represented most often among humanities majors, at intermediate rates in the social sciences, and least among technical majors. The two other disorders in this group were also most frequent in the families of prospective humanities majors but did not reach significance (ADHD, p
0.10; PTSD, p
0.31). From the second group, Alzheimer's approached significance but did not reach it (p
0.069). The incidence of Parkinson's, stroke, and traumatic brain injury was roughly constant across subject matter interest.
Relationships between neuropsychiatric disorders and intended academic major.
One traditional categorization of intellectual interests groups students into broad categories of science/technology/engineering/mathematical (STEM) disciplines, social sciences, and humanities. Information about a variety of familial disorders had the potential to be predictive of a student's position on that axis. We used the significant associations to define for each student a predisposition to subject matter (PRESUME) score by adding 1 point each for a report of bipolar disorder, depressive disorder, and substance abuse, and subtracting 1 point for a report of a sibling with ASD, resulting in an index that ranged from −1 to +3. The covariation of PRESUME with subject matter preference was strongly predictive of intended academic major (χ2
9.6×10-8) (). The overall technical:nontechnical odds ratio varied from 12
−1) to 1
+2 or +3), a 22-fold range (95% CI, 4-fold to >100-fold). Thus a combination of familial psychopathologies was predictive of a major intellectual dimension.
Relationship between subject matter preference and familial neuropsychiatric disorders.