A study conducted in France has linked higher levels of interferon-gamma (IFN-𝛾) in the blood to the later occurrence of suicidal thoughts. Additionally, elevated interferon-gamma levels and reduced orexin-A levels were associated with increased depression severity and anxiety symptoms. The findings were published in Psychoneuroendocrinology.
Suicidal thoughts, clinically known as suicidal ideation, often manifest in individuals experiencing severe depression. The intense emotional pain associated with depression can lead these individuals to view death as an escape from their suffering. The connection between depression and suicidal ideation is well established, with untreated or poorly managed depression recognized as a major risk factor for suicide.
However, not everyone with depression experiences suicidal thoughts. For those who do, immediate support and intervention are crucial, as they can literally mean the difference between life and death. Unfortunately, it is often difficult to detect suicidal ideation. Everyday interactions with individuals who have suicidal thoughts typically do not reveal the presence of these thoughts, making them hard to notice. This underscores the need for a more reliable way to detect or even predict suicidal ideation.
Study author Aiste Lengvenyte and her colleagues aimed to determine whether blood concentrations of proteins associated with inflammation, vascular homeostasis, growth, and sleep could predict suicidal ideation and depression severity six months later. They focused on a group of 32 proteins present in the blood.
The study involved 149 individuals seeking treatment for depression, who were recruited from an academic hospital in France between 2016 and 2018. These participants, aged 18 to 65, had been referred for consultation due to suicidal ideation, a suicide attempt, or depression. All participants were diagnosed with either major depressive disorder or bipolar disorder, with their most recent episode being depression. Of the participants, 71% were female, and their median age was 46 years.
At the start of the study, participants provided blood samples and completed a set of assessments, including an interview with a mental health professional. Suicidal ideation was assessed at the start of the study and again six months later using the Columbia-Suicide Severity Rating Scale. Additionally, a clinician rated the participants on the Inventory of Depressive Symptomatology (IDS-30c) at both time points.
The results indicated that, at the start of the study, higher serotonin levels in blood plasma were associated with lower depression severity and reduced suicidal ideation. However, these serotonin levels were not linked to depression severity or suicidal ideation six months later.
Suicidal ideation six months after the study began was associated with interferon-gamma levels measured at the study’s start, as were atypical psychiatric symptoms. However, the correlation with atypical symptoms disappeared when tobacco and antidepressant use were considered.
Overall, after accounting for various factors that could confound the associations between blood biomarkers and psychiatric symptoms six months later, only the correlation between interferon-gamma levels at the study’s outset and later suicidal ideation remained significant.
Higher levels of interferon-gamma and lower levels of orexin-A at the start of the study were linked to more severe depression symptoms six months later. These levels were also associated with higher atypical and anxious symptom levels.
“These findings highlight the potential utility of peripheral blood biomarkers in identifying individuals at risk of unfavorable depression outcomes,” the study authors concluded.
The study explores the possibility of predicting suicidal ideation in advance using blood biomarkers. However, it is important to note that the dropout rate was high: while 149 participants provided data six months after the study began, 266 participants initially enrolled. This high attrition rate could have influenced the results.
The research, “Baseline circulating biomarkers, their changes, and subsequent suicidal ideation and depression severity at 6 months: a prospective analysis in patients with mood disorders,” was authored by Aiste Lengvenyte, Fabrice Cognasse, Hind Hamzeh-Cognasse, Maude Sénèque, Robertas Strumila, Emilie Olié, and Philippe Courtet.