Summary: Researchers found that, on average, women who engage in self-injury tolerate more pain than those who do not. Brain imaging showed stronger connectivity between regions that perceive pain and regions that regulate or dampen pain signals, suggesting a more effective pain-modulation system in people who self-harm.
Source: Karolinska Institute
Researchers at Karolinska Institutet in Sweden have identified neural differences that may help explain why some people who self-injure report lower sensitivity to pain. The study points to stronger pain inhibition and greater integration of pain-modulatory brain networks as possible contributors to reduced pain perception among people who self-harm—a finding that could inform clinical care and therapeutic conversations.
The results are published in the journal Molecular Psychiatry.
While most people avoid painful experiences, a subset of adolescents and young adults engage in nonsuicidal self-injury (NSSI). Self-harm is often linked to psychiatric conditions such as anxiety and depression, but not everyone with these diagnoses self-injures. Understanding neurobiological differences in pain processing may clarify why pain does not always deter such behavior.
“We have long sought to understand how people who self-injure differ from those who do not and why pain alone may not prevent self-injury,” says Karin Jensen, researcher and group leader at the Department of Clinical Neuroscience, Karolinska Institutet, and the study’s corresponding author. Previous research indicated lower pain sensitivity in people who self-harm, but the underlying mechanisms remained unclear.
Tolerating higher levels of pain
To investigate these mechanisms, the team compared pain modulation in 41 women who had engaged in self-injury at least five times in the previous year with 40 matched women without a history of self-injury. Participants were aged 18–35 and completed laboratory pain testing at Karolinska University Hospital during 2019–2020. They rated pain from brief pressure and heat stimuli on two occasions, and their brain activity during pain was recorded using functional MRI.
On average, women with a history of self-injury tolerated higher levels of experimentally induced pain than the control group. Functional brain imaging showed distinct differences in network activation: participants with self-injury behavior exhibited stronger functional connections between regions responsible for sensing painful stimuli and those involved in inhibiting or modulating pain.
Importantly, the differences in pain modulation were not tied to the frequency, duration, or specific method of self-injury reported by participants. This suggests that the observed neural pattern—more effective central down-regulation of pain—may reflect an underlying trait rather than a consequence of particular self-injury behaviors.
Clinical relevance and implications
“Our findings indicate that enhanced pain inhibition may act as a risk factor for self-injury,” says Maria Lalouni, researcher at the Department of Clinical Neuroscience and co–first author of the study. The results shed light on brain differences in people who self-injure and could help clinicians better tailor care. Understanding that some individuals have an increased capacity to down-regulate pain may inform assessment, psychoeducation, and treatment planning when addressing self-injurious behavior.
The researchers note limitations: participants with self-injury reported higher rates of psychiatric comorbidities and were more likely to use medications such as antidepressants compared with controls. These factors were accounted for in the analysis, but they remain important considerations when interpreting the results.
Funding: The study received support from the Swedish Research Council, the Strategic Research Area Neuroscience (StratNeuro) at Karolinska Institutet, and a donation from Leif Lundblad to pain research.
About this pain and self-harm research news
Author: Press Office, Karolinska Institutet
Source: Karolinska Institute
Contact: Press Office – Karolinska Institutet
Image: The image is in the public domain
Original Research: Open access. “Augmented pain inhibition and higher integration of pain modulatory brain networks in women with self-injury behavior” by Maria Lalouni et al., Molecular Psychiatry.
Abstract
Augmented pain inhibition and higher integration of pain modulatory brain networks in women with self-injury behavior
People who engage in nonsuicidal self-injury (NSSI) often show reduced pain sensitivity compared with those who do not self-injure, but the neural basis for this difference is unclear. This case–control study examined which components of the pain-regulatory system might explain decreased pain sensitivity in NSSI.
The study included 81 women aged 18–35 (mean age 23.4 years), of whom 41 had NSSI and 40 were healthy controls. Quantitative sensory testing assessed heat pain thresholds and tolerance, pressure pain thresholds, conditioned pain modulation (a measure of central pain inhibition), and temporal summation (a measure of pain facilitation). Pain-evoked brain responses were measured with fMRI during thermal stimulation.
Participants with NSSI demonstrated stronger central down-regulation of pain on conditioned pain modulation testing compared with controls. Neural responses to painful stimuli revealed greater integration between nociceptive regions and pain-modulatory networks in the NSSI group. Consistent with prior work, both pressure and heat pain thresholds were higher in participants with NSSI, yet these pain measures did not correlate with clinical characteristics of NSSI.
Overall, augmented pain inhibition and increased involvement of pain-modulatory brain networks may represent a pain-insensitive endophenotype that is associated with an elevated risk for developing self-injurious behavior. This insight could help shape clinical approaches to assessment and treatment for those who self-harm.