A 2016 study in the journal Psychoneuroendocrinology confirms that high levels of inflammatory cytokines in the blood are linked to higher risk of depression following a stroke.
The study, by Hee-Ju Kang and colleagues, followed 222 stroke sufferers for one year. Two weeks following the stroke, their levels of inflammatory cytokines IL-6 and IL-18 were measured. They were also assessed for depression both at the two-week point and one year later. The researchers also observed whether or not the participants were treated with statins, which are often prescribed to lower stroke risk and also have anti-inflammatory effects.
Those participants who had depression following their strokes (either at two weeks or at one year) tended to be older, to have a history of depression or stroke, to have a more severe stroke, and to have a stroke location toward the front of the brain.
Having any depression following the stroke was associated with higher levels of IL-6 and IL-18. This was particularly true of those participants who were not taking a statin. Among those taking statins, the statins may have interfered with the link between inflammatory cytokines and post-stroke depression. In the statin group, the only significant finding was a link between levels of IL-6 and depression at the two-week mark.
Patients with bipolar disorder often show increases in signs of inflammation, including levels of the proteins IL-2, IL-4, Il-6, IL-10 and tumor necrosis factor in their blood. Lithium is the most effective treatment for bipolar disorder, but it is not yet clear how it works. A recent study by researcher Joao de Quevado and colleagues determined that lithium can reduce the same inflammatory markers in rats.
Rats were treated with amphetamine to induce mania-like behavior, which was accompanied by increases in some of the same inflammatory markers in the blood and brain that are increased in people with bipolar disorder. Lithium treatment reduced both the manic behavior and levels of these inflammatory proteins in the rats.
The researchers concluded that lithium may treat mania by reducing inflammation.
Researchers believe there is a link between diabetes and depression. Some drugs used to treat type II diabetes and its associated inflammatory symptoms have been found to improve depression as well. These include metformin, rosiglitazone, and pioglitazone. A recent study by Natalie Rasgon and colleagues explored the effects of pioglitazone treatment on people with insulin resistance, insulin sensitivity and/or pre-diabetes and ongoing depression. The researchers hoped to find that adding pioglitazone to the patients’ regular antidepressant regimen might improve depression by reducing inflammation.
The study also touched on the role of telomere length in mental and metabolic disorders. Telomeres are repeated DNA sequences that sit at the end of chromosomes and protect them during cell replication. Telomeres get shorter with aging and with psychiatric illnesses. In the study, telomere length was used to predict whether patients’ depression would improve.
Rasgon and colleagues found that in those patients taking both pioglitazone and antidepressant treatments (compared to those who received a placebo in addition to their antidepressants), longer telomeres predicted better antidepressant response. This suggests that telomere length could be used as a biomarker—that is, measuring a patient’s telomere length could reveal whether that patient’s depression is likely to respond to an anti-inflammatory treatment such as pioglitazone. The research was presented at a 2015 scientific meeting.
Drug treatment for major depression can produce remission in 35–50% or patients. The others may need additional interventions, and some mind-body techniques have been successful. A recent randomized study by Anup Sharma and colleagues found that Sudarshan Kriya Yoga (SKY) decreased depression at one and two months when added to participants’ regular treatments. Participants who received the yoga treatment also showed reductions in inflammation in the blood, including lower levels of the inflammatory proteins TNF-alpha, IL-10, and CRP.
Inflammation has been linked to both unipolar and bipolar depression. New research shows that anti-inflammatory treatments may reduce bipolar depression, for which few treatments exist.
Researchers led by Jonathan Savitz divided people with bipolar depression into four groups. One group received two placebos, another received minocycline (a drug with neuroprotective and immune-modulating properties) plus a placebo, the third received aspirin plus a placebo, and the final group received both minocycline and aspirin. Of the 64 participants, those who took both minocycline and aspirin were most likely to respond to treatment and to enter remission. In people with body mass indexes (BMIs) above the median of 30, a sign of greater inflammation, 100% of those who received both anti-inflammatory drugs responded to treatment, compared to 36% of those who received aspirin alone, 33% of those who received minocycline alone, and 25% of those who received two placebos.
Dosages of the drugs were 100mg twice a day for minocycline and 81mg twice a day for aspirin. Savitz and colleagues believe that aspirin and minocycline must work particularly well together, and are modifying their study to more directly compare use of the two anti-inflammatory drugs together to the absence of anti-inflammatory treatments.
People with post-traumatic stress disorder (PTSD) often experience fearful memories of the trauma they witnessed. Researchers are working to determine the neurobiological basis for these persistent fear memories in order to better treat PTSD. Current treatments mainly target the central nervous system. Because many people with PTSD have elevated levels of pro-inflammatory immune molecules in their blood, there has been a recent push to determine whether targeting that inflammation may be another way of treating PTSD.
A recent study by researchers Matthew Young and Leonard Howell used an animal model to learn more about the link between trauma, inflammation, and fear memories. The researchers exposed mice to a trauma that produced both a persistent fear response and an increase in inflammatory molecules in the blood. Some of the mice were also given antibodies to neutralize the inflammatory immune response. When the mice were exposed to a cue meant to remind them of the trauma, levels of the inflammatory molecule IL-6 spiked again. When the mice were given antibodies to neutralize IL-6 just before being exposed to the cue, they produced less of a fear reaction.
The researchers, who presented their work at a scientific meeting in December, concluded that traumatic experiences produce not only persistent fearful memories, but also an immune reaction. They believe that the spike in IL-6 following trauma plays a role in the persistence of those memories, and that elevated IL-6 in the blood may explain symptoms of PTSD and other disorders that involve fear learning (such as phobias).
Many studies have found links between levels of inflammatory molecules in the blood and depression or depressive symptoms. There has been less research about inflammation in the brain and its possible role in depressive illness. Improvements in positron emission topography (PET) scan technology now allow for better brain imaging that can reveal when microglia are activated. (Microglia serve as the main immune responders in the central nervous system.)
A study by researcher Jeffrey Meyer found evidence of microglial activation in several brain regions (including the prefrontal cortex, the anterior cingulate cortex, and the insula) in people in an episode of depression who were not receiving any treatments. Participants with more microglial activation in the anterior cingulate cortex and insula had more severe depression and lower body mass indexes.
Meyer, who presented this research at a scientific meeting in December, called it strong evidence for brain inflammation in depressive episodes, and suggested that treatments that target microglial activation would be promising for depression.
However, at the same meeting, researcher Erica Richards reported that she had not been able to replicate Meyer’s results. Her research, which included depressed participants both on and off medication and non-depressed participants, found that depressed participants did show more inflammation in the two brain regions she targeted, the anterior cingulate and the subgenual cortices, but this difference did not reach statistical significance, particularly when patients taking antidepressants were included in the calculations. Richards hopes that with a greater sample size, the data may show a significant difference in brain inflammation between depressed and non-depressed participants.
The Course and Outcome of Bipolar Youth study, or COBY, has been collecting information on young people with bipolar disorder and tracking their symptoms into adulthood since 2000. A 2015 study by Benjamin I. Golstein in the Journal of Clinical Psychiatry analyzed COBY data, identifying links between higher than average levels of inflammatory markers measured in the blood and participants’ histories of illness and familial risk factors.
High levels of the inflammatory marker hsCRP were associated with longer duration of illness, substance use disorder, and family history of suicide attempts or completed suicides. High levels of TNF-alpha were linked to suicide attempts, self-injury behaviors, and family history of substance use disorders. IL-6 was also linked to family history of substance use disorders.
There were also links between inflammatory markers and participants’ symptoms over the 6 months leading up to the blood tests. Levels of the inflammatory marker TNF-alpha were linked to the percentage of weeks patients had psychotic symptoms. Levels of IL-6 were associated with percentage of weeks with subthreshold mood symptoms and also with any suicide attempt. Levels of HsCRP were linked to maximum severity of depressive symptoms.
It is possible that targeting the elevated levels of inflammatory markers with anti-inflammatory treatments could improve patients’ response to treatments, but this topic requires further study.
A 2012 study by Geoge I. Papkostas and colleagues found that 15mg/day of the nutritional supplement l-methylfolate calcium (a form of the B vitamin folate that the body can more readily use) improved depression in people who had not responded adequately to treatment with a selective serotonin reuptake inhibitor (SSRI) antidepressant. In a follow-up study by Richard C. Shelton and colleagues published in the Journal of Clinical Psychiatry in 2015, the same researchers further analyzed these data and found that l-methylfolate worked better in patients who were overweight (with body mass indexes (BMIs) of 30 or above) and those who had higher than average levels of inflammation at the beginning of the study. Inflammatory markers linked to greater improvement with l-methylfolate included TNF-alpha, IL-8, high sensitivity CRP, and leptin. In overweight participants, higher than average levels of IL-6 were also linked to more improvement on l-methylfolate.
A 2016 study by Peter S. Bloomfield and colleagues in the American Journal of Psychiatry used PET scans to compare the activity of microglia, immune cells in the central nervous system, in healthy controls, people with schizophrenia, and those at high risk for the illness. It found that both people with schizophrenia and those at high risk had greater brain inflammation than the healthy controls.
The study was the first to show that microglial activity was elevated in people at high risk (who showed some preliminary symptoms of schizophrenia). The finding had a large effect size.
Microglial activity was also correlated with symptom severity in the high-risk participants. Increased microglial activity was not linked to depression, suggesting that it is specific to the development of psychosis.
These findings resemble those of other recent studies showing increased inflammation in people at high risk for psychosis.
The study suggests that increased microglial activity occurs before a first episode of psychosis. That means it could help identify people who may develop schizophrenia. The findings also suggest that anti-inflammatory treatment could theoretically be used to prevent psychosis.