We found that harm avoidance (HA) was higher in SCZ than SCZ, CON, and CON-SIB, while SCZ-SIB was also significantly higher than the control groups. The intermediate level of harm avoidance in non-psychotic siblings provides evidence that HA may be an endophenotype for schizophrenia. These findings are consistent with prior studies examining individuals with schizophrenia (Kurs et al., 2005
) and their first-degree relatives (Calvo de Padilla et al., 2006
When examining the association between HA and psychopathology and neurocognition, we found that negative symptoms and HA were highly correlated in SCZ and SCZ-SIB. This is not surprising given that HA is characterized by inhibition and fatigability, both of which may be subclinical manifestations of negative symptoms. This lends support to the pervasive role of negative symptoms in individuals with schizophrenia (Fenton & McGlashan, 1991
) and elevated negative symptomatology in first-degree relatives (Glatt et al., 2006
). Also, we found a higher prevalence of SCZ configured as having high harm avoidance and low reward dependence or “Hr,” when compared to SCZ-SIB, CON, and CON-SIB. This indicates that individuals with schizophrenia have a higher prevalence of personalities characterized as socially detached and amotivated. Although the value of “Hr” in SCZ-SIB was intermediate between SCZ and CON-SIB, the difference between SCZ-SIB and CON-SIB did not reach statistical significance (p=.13). Thus, the evidence that the “Hr” configuration may be a schizophrenia endophenotype is unclear.
Our findings support previous research on character, which found that individuals with schizophrenia had lower SD and lower CO than controls (Guillem et al., 2002
). Also, individuals with schizophrenia were frequently configured as having low SD, low CO, and high ST or “scT,” which is indicative of a struggle with identity, lack of empathy, and greater magical ideation. These results support prior research indicating that- low average values of self-directedness and cooperativeness, and high average values of self-transcendence represent “schizotypy” (Cloninger et al., 1993
The Venn diagram () illustrates that individuals with schizophrenia were most frequently configured as having asociality (Hr), schizotypy (scT), and neurocognitive deficits. Notably, 20% of the individuals with schizophrenia had a combination of asociality and neurocognitive deficits, but not schizotypy. This suggests that asociality may drive or actuate the deficits in neurocognition, or vice versa. Thus, treatments that decrease HA, such as cognitive behavioral therapy and antidepressants (Abrams et al., 2004
), could potentially reduce risk of schizophrenia. indicates that 85.7% of individuals with schizophrenia met at least one of our three sets of risk factors, which suggests an excellent sensitivity for detecting vulnerability for schizophrenia. The results also suggest that non-psychotic siblings did not receive a discrete “transmission” of schizotypy, but rather individually inherited personality traits, so that configurations like Hr (e.g., social anxiety, isolation) impacted neurocognition and psychobiological character traits in a nonlinear fashion: that is, particular configurations of these variables are critical for risk, not the sum of their average effects.
The profile of character in SCZ-SIB was distinguishable from the profile in SCZ. SCZ-SIB scored higher than SCZ on the measures of SD and CO, while they were similar on ST. Furthermore, the configuration of high SD, high CO, and low ST (SCt) was significantly more prevalent in SCZ-SIB, CON, and CON-SIB when compared to SCZ (). A similar pattern was present when the character configuration was SCT. High SD and CO in non-psychotic siblings reflects a highly goal-directed, responsible, and empathetic character.
These results are consistent with Bora and Veznedaroglu (2007)
who reported high levels of self-directedness and cooperativeness in non-psychotic siblings. They suggested that relatives may develop greater responsibility, goal-orientation, or cooperativeness by stepping into a caregiving role. This is consistent with research indicating that siblings develop personal gains from coping with the challenges of schizophrenia (Smith & Greenberg, 2008
). An alternative explanation is that self-directedness is a heritable personality trait that protects individuals at risk for schizophrenia from developing psychosis (Gillespie et al., 2003
The hypothesis that specific domains of character are potentially protective against the risk of schizophrenia is supported by our findings that SD and CO were highly correlated with crystallized IQ and working memory in SCZ-SIB, and were largely uncorrelated with psychopathology and neurocognition in SCZ, CON, and CON-SIB. This suggests that SD and CO could be protective of crystallized intelligence and other neurocognitive functioning specifically in the non-psychotic siblings. Thus, higher levels of neurocognition, a more maturely developed character, and a positive correlation between them may act as mechanisms of resilience or protection against schizophrenia liability. For instance, high levels of SD and CO could be protective against high levels of ST, which are highly correlated with positive symptoms in SCZ and SCZ-SIB. Additionally, we found that SD and CO were inversely correlated with disorganized and negative symptoms in non-psychotic siblings, which is consistent with research suggesting that a mature character profile in siblings might be protective against their own heritability to psychopathology (Bora & Veznedaroglu, 2007
There were some limitations to this study. First, the sample was highly selective as all participants agreed to participate in a larger study that required completion of clinical and cognitive testing and brain imaging. Second, the majority of individuals with schizophrenia were male. Thus, our results may have poorly reflected the temperament and character of siblings of females with schizophrenia. Lastly, we may not have sufficient power to detect weak relationships between group membership and temperament and character or between the dimensions of personality and psychopathology and neurocognition in this study. Future research should attempt to replicate this study without a gender bias in a larger sample and explore whether particular TCI domains or configurations act as mechanisms of protection against developing schizophrenia in populations at elevated risk for developing the disorder.