Crime Causation: Biological Theories

Another pathway that has been investigated as a potential determinant in the etiology of violence is prenatal factors. The prenatal period presents a nine-month window in which the developing fetus may be exposed to a variety of stressors and agents. There are reasons to suspect that these stressors or agents may operate differently depending on when they are introduced. Recently, an increasing amount of attention has been paid to pinpointing the gestational periods of highest risk for negative outcomes. One such teratogen that has been extensively investigated is the timing of maternal influenza exposure in relation to negative outcomes in the exposed fetuses.

Maternal prenatal influenza. In Helsinki, our research group reported that second-trimester maternal influenza significantly increased the risk of adult schizophrenia (Mednick et al., 1988) and major affective disorder (Machon and Mednick) in the exposed fetuses. The data have been replicated in numerous studies in various countries.

The "second-trimester schizophrenics" were interviewed and found to differ from non-influenza exposed schizophrenics in that their symptom picture was dominated by suspiciousness and delusions (Machon and Mednick). As both Volavka and Hodgins suggest, delusional paranoid individuals are characterized by elevated levels of violent behavior. Mednick, Machon, and Huttenen hypothesized that a common etiological link between schizophrenia and violence may be a disturbance in fetal neural development in the second trimester.

Accordingly, Mednick, Machon, and Huttenen (1996) hypothesized that maternal influenza during the second trimester was associated with an increased risk for violent offending, but not property offending among exposed fetuses. To test this hypothesis, the Finnish criminal register was searched for all of the Helsinki residents born in the nine months after the 1957 influenza epidemic. The results indicated that property crime was not significantly associated with period of exposure to the influenza virus. Individuals who had been exposed to the influenza virus during the second trimester of gestation, however, were significantly more likely to have a criminal conviction for violence than individuals who were exposed to the influenza virus during the first or third trimesters of gestation or not exposed to the virus at all.

The impact that the influenza virus has on fetal neural development, either negative or neutral, appears contingent upon the timing of the virus, relative to the stage of gestation. It may also be difficult if not impossible to identify a specific month or trimester associated with the highest risk of negative outcome in cases where the teratogen is present throughout development, or when the long-term effects of the teratogen may linger and have residual effects throughout the period of gestation. Introduction of some types of teratogens, such as illegal drugs, alcohol, and nicotine, may represent substances that, regardless of when they are introduced, could potentially be harmful to the exposed fetus. Much attention has recently been paid to the association between maternal smoking during pregnancy and negative behavioral outcomes among exposed fetuses. These negative outcomes include impulsivity and attention problems. Prenatal nicotine exposure has also been associated with criminal offending.

Maternal prenatal smoking. An investigation conducted in Finland by Rantakallio and colleagues, examined the criminal records of 5,966 members of a birth cohort and found that prenatal maternal smoking predicted to criminal offending at age twenty-two. These findings persisted after controlling for the effects of social variables such as socioeconomic status. With these recent studies in mind, Brennan, Grekin, and Mednick investigated the association between maternal smoking and criminal violence using a Danish birth cohort of 4,129 males. It was hypothesized that maternal smoking would be related to an increased risk of violent offending among males. One of the major strengths of the study was that maternal prenatal smoking was assessed through interviews during the pregnancy as opposed to retrospectively. Moreover, the study relied on the Danish criminal register to identify cases where the individuals were arrested for property or violent offenses.

The findings indicate a linear dose-response relationship between the number of cigarettes the mother smoked on a daily basis in her third trimester of pregnancy and the percent of offspring who became violent offenders. This relationship persists despite controlling for various potential confounds such as socioeconomic status, parental psychiatric hospitalization, and father's criminal history.

The recent finding that maternal smoking during pregnancy is linked to criminal violence in exposed offspring, along with Rantakallio's study, suggests the possibility that chemicals contained in cigarette smoke may alter fetal brain neurochemistry. Moreover, exposure to cigarette smoke prenatally may increase risk for asphyxia.