Journal Digest: Events Before First-Episode Psychosis; Poor Neuron Insulation and Autism; Memory Suppression and Adaptation After Trauma

Individuals with first-episode psychosis are much more likely to have experienced a threatening life event in the previous year compared with people without psychosis, reports a study in Schizophrenia Bulletin.

Researchers at Kings College London recruited 374 adults with first-episode psychosis and used the Life Events and Difficulties Schedule (LEDS) to ascertain their adverse life experiences. They also assessed 301 adults who had not experienced psychosis (controls). In all, 253 people with first-episode psychosis and 301 controls completed the LEDS interview.

People with first-episode psychosis were about three times as likely as controls to report experiencing at least one threatening event in the prior year. They were about four times as likely to have experienced threatening life difficulties (events that span at least four weeks). This effect was greatest for events and difficulties categorized as intrusive (defined by authors as those involving an element of control and/or intention to harm, such as physical assault or rape).

The researchers found evidence of a cumulative effect for these events and difficulties: the more an individual’s exposure in the past year, the greater the psychosis risk.

The researchers noted that difficult life events likely impact mental well-being on a broad level, but these findings tentatively suggest that events involving threat and violence are particular risk factors for disorders that include paranoia and hallucinations.

A study appearing in Nature Neuroscience suggests that people with autism spectrum disorder (ASD) may have problems producing myelin—a fatty substance that helps insulate neurons. Having neurons without proper insulation can result in impaired brain communication.

Researchers at the Lieber Institute for Brain Development in Baltimore and colleagues evaluated two groups of mice for this study. They first assessed mice designed to lack a gene called TCF4. This mutation is responsible for a rare disorder called Pitt-Hopkins syndrome, which has many ASD-like symptoms. They found that these mice had defects in the expression of numerous genes in the oligodendrocytes—the myelin-producing cells in the brain. An analysis of the brain tissue of these mice confirmed that the proportion of myelinated neurons was lower in these animals compared with animals with the TCF4 gene.

The researchers then analyzed other mice genetically modified to express behaviors similar to those of patients with Rett syndrome, another developmental disorder with ASD-like symptoms. They found that these animals also had altered gene expression in the oligodendrocytes.

Finally, the researchers analyzed 15 postmortem brain tissue samples donated from people with ASD. They found that the ASD samples had lower myelin thickness in several brain regions compared with healthy tissue samples.

“Because myelination is a lifelong process, it provides a unique therapeutic opportunity that we can tap into throughout the lifespan,” said senior study author Brady Maher, Ph.D., in a press release. “Along these lines, we are eager to see whether enhancing myelination in these mice can improve their ASD-associated behaviors.”

By conducting behavioral studies of people who experienced the 2015 Paris terrorist attacks, researchers at INSERM in France have shed light on why some people are more resilient to traumatic events than others. The study was published in Science.

The study included 102 individuals exposed to the 2015 Paris attacks—55 individuals with posttraumatic stress disorder (PTSD) and 47 individuals with no PTSD—along with 73 nonexposed individuals (those who were not in Paris during the attacks). The researchers trained the participants to associate specific words with corresponding images. Afterward, the participants were asked to try and suppress some of their learned cues while undergoing an MRI scan. Later, they participated in another visual-based game and reported whenever they had intrusive thoughts related to the suppressed cues.

While all of the participants were able to suppress their learned cues with training, during the visual tasks the participants with PTSD were much more likely on average to recall these cues. The MRI scans showed that this recall corresponded with reduced connectivity among brain regions involved in inhibitory control. The degree of reduced connectivity was not related to the type or severity of the experienced trauma.

The researchers noted that these findings highlight a mechanism by which unwanted memories persist in people with PTSD. They also show why exposure therapy—which asks people to recall their trauma as a means to lessen its impact—is not effective for every patient. ■