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.
Studies have found that inflammatory molecules play a role in depression. A recent study by researcher Yu Sun and colleagues used data from clinical trials of anti-inflammatory drugs to show that these drugs also reduced depressive symptoms. The two drugs, which are administered either by a shot or injection into the skin, each consist of antibodies that target the inflammatory molecule IL-6. Sirukumab is being looked at as a possible treatment for rheumatoid arthritis, while siltuximab is a potential treatment for Castleman’s disease, an illness characterized by enlarged lymph nodes. As part of the clinical trials for these drugs, patients with these illnesses responded to survey questions that assessed symptoms of depression and fatigue.
Among patients who reported that they have at least one depressive symptom most of the time and another symptom at least part of the time, the anti-inflammatory drugs significantly improved depressive symptoms compared to placebo. Even when the patients’ inflammatory illnesses did not respond to the anti-inflammatory treatments, their depressive symptoms did improve (symptoms of fatigue did not). An improvement in depressive symptoms was observed after 6 weeks in patients with Castleman’s disease taking siltuximab, and after 12 weeks in patients with rheumatoid arthritis taking sirukumab.
In the sirukumab study, the level of the inflammatory molecule IL-6 in participants’ blood before the study was linked to the magnitude of improvement in their depressive symptoms during the study. IL-6 is elevated in many patients with unipolar and bipolar depression. It is possible that antibodies that target IL-6 could be used to treat primary depression (in the absence of other inflammatory disorders).
Stress increases the risk of psychiatric illnesses such as major depression and post-traumatic stress disorder. Not everyone who experiences stress goes on to develop these illnesses, though. Researchers are currently trying to find out why, exploring treatments that might increase resilience and prevent mental illnesses.
Animal research is often used to study depression. Mice exposed to certain stressors behave in ways that resemble human depression—like giving up faster when they’re forced to tread water, or withdrawing from activities they once enjoyed, like eating sucrose. In a recent study by researcher Christine Denny and colleagues, mice were injected with either saline or ketamine, a rapid-acting antidepressant, and one week later they were exposed to triggers that typically produce a depressive response. Mice who received the saline injection still got depressed when, for example, they were repeatedly forced to confront a dominant mouse. But mice who received ketamine injections did better, maintaining their motivation and not showing signs of depressive behavior following the stress. The researchers concluded that ketamine may have a protective effect against stress.
Editor’s Note: These results are remarkable because ketamine’s effects are typically short-lived.
Brain-derived neurotrophic factor (BDNF) is a protein that protects neurons and aids with learning and memory. BDNF levels are low in people with depression, and every type of antidepressant treatment increases BDNF, including different types of medications, electro-convulsive therapy, repeated transcranial magnetic stimulation (rTMS), exercise, atypical antipsychotic drugs used to treat bipolar depression, omega-3 fatty acids, and ketamine. New research shows that sleep deprivation, which is sometimes used to rapidly improve depression, also increases BDNF.
A study by researcher Anne Eckert and colleagues found that partial sleep deprivation (preventing sleep only during the second half of one night) increased BDNF levels in the blood the following day. Those participants who responded well to the sleep deprivation were found to have BDNF levels that fluctuated more throughout the day before the sleep deprivation compared to participants who did not respond well to the sleep deprivation, whose BDNF levels were relatively stable.
The research, which was presented at a scientific meeting in 2015, suggests that sleep deprivation in depressed patients increases BDNF, and that such increases are an important function of any antidepressant treatment.
Researchers are looking for better ways of predicting whether children at risk for bipolar disorder will go on to develop the illness. A 2015 study by David Axelson and colleagues in the American Journal of Psychiatry reported that in the offspring of parents with bipolar disorder, diagnoses of sub-threshold mania, depression, and disruptive behavior disorders were associated with subsequent diagnosis of full-blown Bipolar I or Bipolar II disorders six to seven years later.
More recently, in an article by Danella M. Hafeman and colleagues in the American Journal of Psychiatry, the same group of investigators has examined how symptoms (rather than categorical diagnoses, as in the earlier study) predict the development of bipolar disorder. In children and adolescents at high risk for bipolar disorder (because they have a parent with the disorder) three types of symptoms were the best predictors of later bipolar disorder: anxiety/depression at the time participants entered the study, unstable mood or irritability both when entering the study and shortly before a bipolar diagnosis, and low-level manic symptoms observed shortly before diagnosis.
The earlier the age at which a parent was diagnosed with a mood disorder, the greater the risk that the offspring would also be diagnosed with bipolar disorder. Youth with all four risk factors (anxiety or depression, mood changes, low-level mania, and a parent who was diagnosed with a mood disorder at an early age) had a 49 percent chance of developing bipolar disorder, compared to a 2 percent chance among those without those risk factors.
Childhood onset of bipolar disorder and long delays until first treatment for depression or mania are both significant predictors of a poor outcome in adulthood compared to adult onsets and shorter delays to treatment. Read more
A recent study confirms that women who are depressed during pregnancy are more likely to experience adverse pregnancy outcomes such as preterm or cesaerean delivery and small or underweight babies. However, antidepressant treatment improved outcomes for pregnant women with depression.
The 2016 study by Kartik K. Venkatesh and colleagues in the journal Obstetrics & Gynecology included 7,267 women who gave birth after at least 20 weeks of pregnancy. About 11% of the women screened positive for depression during their pregnancy. Depressed mothers-to-be were more likely to give birth before 37 weeks and before 32 weeks compared to nondepressed mothers-to-be. The depressed women were also more likely to deliver small babies or babies weighing under 2500g.
About 7% of the women in the study received antidepressant medication. Compared to nondepressed women, the women taking antidepressants did not have greater rates of early delivery or small babies. However, the authors caution that because so few women received antidepressants, the study does not reveal whether antidepressants improve outcomes for depressed pregnant women.
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.
Vitamin D3 tends to be low in children and adolescents with mania, but supplements may help. In a small open study published in the Journal of Child and Adolescent Psychopharmacology in 2015, Elif M. Sikoglu and colleagues administered 2000 IU of vitamin D3 per day to youth aged 6–17 for eight weeks. Sixteen of the participants had bipolar spectrum disorders (including subthreshold symptoms) and were exhibiting symptoms of mania. Nineteen participants were typically developing youth.
At the beginning of the study, the youth with bipolar spectrum disorders had lower levels of the neurotransmitter GABA in the anterior cingulate cortex than did the typically developing youth. Following the eight weeks of vitamin D3 supplementation, mania and depression symptoms both decreased in the youth with bipolar spectrum disorders, and GABA in the anterior cingulate cortex increased in these participants.
Editor’s Note: GABA dysfunction has been implicated in the manic phase of bipolar disorder. While larger controlled studies of vitamin D supplementation are needed, given the high incidence of vitamin D deficiency in youth in the US, testing and treating these deficiencies is important, especially among kids with symptoms of bipolar illness.
Scientists have known for some time that heightened activity of dopaminergic neurons (neurons in the midbrain that contain the neurotransmitter dopamine) can make people vulnerable to depression. New research in animals suggests for the first time that noradrenergic neurons (those that contain the neurotransmitter norepinephrine) control the activity of dopaminergic neurons and that these noradrenergic neurons can make the difference between vulnerability to depression or resilience to stress. The research, published by Elsa Isingrini and colleagues in the journal Nature Neuroscience in 2015, showed that animals that cannot release norepinephrine are vulnerable to depression following chronic stress, but increasing the production of norepinephrine increases the animals’ resilience and reduces depression.
These findings may open up new avenues to treatment that target norepinephrine rather than or in addition to dopamine or serotonin, which is targeted by SSRI antidepressants, or selective serotonin reuptake inhibitors.
Many studies have linked depression and cardiovascular problems. The solutions may also be linked. A new study found that patients with depression and acute coronary syndrome saw their depression improve most when they took the selective-serotonin reuptake inhibitor (SSRI) antidepressant escitalopram and statins (used to lower cholesterol), while depression improved least among patients who took neither type of drug. Statin use was linked to improvement in depression after one year, while escitalopram was not. In a subset of the study, use of lipophilic statins in particular was linked to improvement in depression.
The study, published in 2015 by S.W. Kim and colleagues in the journal Translational Psychiatry, suggests that statins can improve depression regardless of antidepressant use, but combining statins with an SSRI may have an even more powerful effect on depression.