The brain roots of sexual offenses: a focus on pedophilic and sadistic offenders. Conclusions of a systematic review and meta-analysis.

Introduction. Employing neuroimaging techniques enables an adequate understanding of the neural correlates that underlie the perpetration of different types of offenses, such as sexual offenses. We conducted a systematic review and meta-analysis that analyzed whether there are structural and functional brain differences when comparing sex offenders and controls. Methods. The systematic review followed the PRISMA framework using Scopus, PubMed, Web of Science, PsycInfo, and Embase, complemented with the snowball technique. It was further complemented with a meta-analytic approach conducted using random effects, including mean comparisons and correlational outcomes for structural data, as well as activation likelihood estimation (ALE) for functional data. Results. From a total of 4,506 articles initially identified, 55 studies were selected. Most of the research focused on pedophilic offenders (child abuse), with only a few studies paying attention to sex offenders with a history of offenses against adults (rapists). Computed tomography research allowed us to conclude that, among sex offenders, pedophilic offenders with child abuse offenses presented more widespread brain alterations (unspecified location), followed by sex offenders with a history of offenses against adults, particularly those scoring high in sadism. Additionally, magnetic resonance imaging studies highlighted that pedophilic offenders presented reduced gray matter volume in the left dorsal prefrontal cortex, the insula (bilaterally), and the left temporal lobe compared to controls (non-offenders). They also showed reduced white matter in the left frontal lobe, as well as bilaterally in the temporal and parietal lobes. Functional analyses revealed that pedophilic offenders presented a reduced activation of the left dorsal posterior cingulate gyrus and the precuneus during inhibitory tasks compared to pedophilic individuals without offenses and controls. Furthermore, during exposure to child nudity stimuli, pedophilic offenders presented higher activation in the right cerebellum and inferior temporal gyrus, as well as the left inferior and middle occipital gyri, compared to controls. However, due to the scarce number of studies involving sex offenders without pedophilia or offenses against children, it is especially difficult to draw conclusions about the brain functioning of this type of offender. Nevertheless, differential activation of the right anterior temporal cortex during moral transgression tasks allowed differentiation between sadistic and non-sadistic sex offenders with a history of offenses against adults. Conclusions. These results reinforce the need to further investigate crucial brain regions and structures that underlie these types of offenses. Lastly, they can also help guide future neuroimaging studies to focus on specific brain regions and structures.