A study discovered differences in pain modulation in the brains of self-injurers

Researchers at Sweden's Karolinska Institute in Solna believe they have found why self-injurers feel less pain than others. A better effective pain-modulation system appears to be the key, which could aid those seeking self-harm treatment.

The findings of the research were published in Molecular Psychiatry journal.

Maximum people try to avoid pain, but some, particularly adolescents and young adults, can cause physical harm inadvertently. Although self-harm is closely identified with other mental issues such as depression and anxiety, not everyone affected by such a condition engages in self-harm.

"We've long tried to understand how people who self-injure vary from others, or why pain alone isn't a strong deterrent," says Karin Jensen, corresponding author of the study and researcher and group leader at Karolinska Institutet's Department of Clinical Neuroscience. "Previous research has found that those who self-harm are usually less sensitive to pain, however the mechanisms underlying this are not fully understood."

In the current study, 41 women who had self-injured at least 5 times in the previous year were compared to 40 women who've not engaged in self-injury habits. In 2019-2020, the women in age group of 18 to 35 were subjected to two laboratory pain exams at Karolinska University Hospital, where they rated the pain they felt from transient heat stimulations and pressure. MRI scans were used to assess their brain activity while experiencing pain.

The researchers have found that self-harming women tolerate more pain on average than controls. Brain scans revealed that there were also differences in activation between groups. Women who self-injure had better connections between brain areas involved in pain perception and those linked to pain modulation when compared to controls.

Another finding was that differences in pain modulation were unrelated to the length, frequency, or mode of self-injury.

"Our findings suggest that good pain modulation is a risk for self-injury behaviour," asserts Maria Lalouni, a Karolinska Institutet researcher and co-first author of the study with Jens Fust, who recently finished his PhD on the project. "It also teaches us more about the differences in brains of people who self-injure,  knowledge that can be used to improve the support offered to people needing treatment for their behaviour, and discussions with patients to help them recognise their self-injury and need for treatment."

One study limitation was that self-injuring women had more psychiatric comorbidities than controls. They also used more drugs, like antidepressants, which the researchers considered in their research.