While it can sometimes take weeks for the effects of antidepressant treatments to appear, intravenous ketamine can produce antidepressant effects in as little as two hours. However, ketamine’s effects fade after three to five days. New animal research by Chi-Tso Chiu et al. explores whether adding lithium to ketamine treatment can produce more sustained antidepressant effects.
Mice who are restrained by being placed in a tube for several hours (chronic restraint stress) exhibit a behavioral and neurochemical profile that resembles human depression. When Chiu and colleagues pretreated these stressed mice with sub-therapeutic doses of lithium (600 mg/L) in their drinking water for several weeks, a sub-therapeutic dose of ketamine (2.5 mg/kg of body weight) was enough to produce robust antidepressant effects in the mice, while neither drug alone was effective at these doses.
The combination of ketamine and lithium also restored the density of spines on the dendrites of neurons in the medial prefrontal cortex. Post-treatment with lithium (1200 mg/L) for several weeks was also successful in extending the effects of a single (50 mg/kg) ketamine injection.
Both lithium and ketamine affect the intracellular signaling pathway mTOR. Ketamine activates the pathway, increasing levels of synaptic proteins and dendritic spine density. It also increases brain-derived neurotrophic factor (BDNF) and the BDNF receptor TrkB. BDNF is important for learning and memory.
When lithium was added to the treatment of the mice with ketamine, the mTOR and BNDF pathways were further activated. Lithium also inhibits the receptor GSK-3, supporting ketamine’s rapid-acting antidepressant effects.
Ketamine treatment can produce oxidative stress, in which toxic free radicals can endanger cells, and the addition of low doses of lithium also completely prevented this neurochemical side effect.
Chiu and colleagues hope that the findings of this study in mice can eventually be applied to research in humans in the hopes of finding a clinical option that would sustain the rapid-onset antidepressant effects of ketamine for the long term.
Researcher Andrea Danese discussed the influence of childhood maltreatment on inflammation in a symposium at the 2014 meeting of the American Academy of Child and Adolescent Psychiatry. Danese indicated that inflammation is part of the normal immune system, which includes the blood brain barrier, recognition of self- versus non-self proteins, activation of cytokines and endothelial cells, and response by phagocytes and acute phase proteins. In an acute phase inflammatory response, the liver secretes proteins including c-reactive protein (CRP) and fibrinogen into the blood, where their levels can be measured.
Normal amounts of inflammation can be protective, while excessive or persistent inflammation can be damaging and pathological. The inflammatory cytokines interferon gamma and tumor necrosis factor (TNF alpha) induce an enzyme called indoleamine oxidase (IDO) that shunts the amino acid tryptophan away from its normal path, which yields serotonin, so that it instead yields kynurenine and then kynurenic acid, which inhibits the action of glutamate at NMDA receptors. Kynurenine can also be hydroxylated and turned into quinolinic acid, which activates glutamate NMDA receptors and causes toxicity.
In addition, inflammatory cytokines such as interleukin six (Il-6) can cross the blood brain barrier and directly influence neurotransmission. Meta-analyses have shown that inflammatory markers CRP, IL-6, IL-1, and IL-1 Ra all increase significantly in depression. A direct demonstration of the relationship between inflammation and depression is the finding that when hepatitis C is treated using the inflammatory treatment interferon gamma, there is about a 30% incidence of depression, which responds to the antidepressant paroxetine.
Stress can also increase the activity of the sympathetic nervous system, driving inflammation, and decrease parasympathetic activity, resulting in further inflammation. In addition, glucocorticoid receptor resistance can develop, enhancing depression, and increasing inflammation. Thus there are multiple ways inflammation can develop.
Danese described a study from New Zealand in which 1000 participants were observed over several decades—from childhood through age 38. The small percentage of participants who experienced maltreatment as children (aged three to eleven) showed a linear increase in CRP in adulthood as a function of their histories of previous child maltreatment. The maltreatment included parental rejection in 14%, sexual abuse in 12%, harsh discipline in 10%, changing caretakers in 6%, and physical abuse in 4%. Childhood maltreatment was also associated with some unfortunate outcomes in adulthood, including lower socioeconomic status, more major depression, more persistent depression, more cardiovascular risk, and more smoking. In other studies, Danese found that compared with controls, patients with depression alone, and patients with maltreatment alone, a greater number of patients with both depression and maltreatment (about 30%) had elevated CRP.
Danese noted that in a study by Ford et al. (2004), recurrent depressions, but not single depressions, were also significantly associated with increased CRP. In a meta-analysis by Nanni et al. in the American Journal of Psychiatry in 2012, Danese and colleagues found that across multiple studies, childhood maltreatment was associated with a twofold increase in the incidence of depression and a twofold increase in the persistence of depression (chronic depression or treatment resistance). The traditional optimal treatment for depression, combined psychotherapy and pharmacotherapy, was also significantly less effective in those with histories of childhood maltreatment. However, psychotherapy alone was equally effective in those with and without childhood maltreatment.
Together these data suggest that childhood maltreatment, partly through an inflammatory pathway, results in multiple difficulties in adulthood, including depression and treatment resistance. These data speak to the importance of attempting to prevent maltreatment in the first place, and ameliorating its consequences should it occur.
Editor’s Note: In a 2014 article in the Journal of Nervous and Mental Disorders, this editor Robert Post and colleagues reported that childhood adversity (verbal, physical, or sexual abuse) is associated with increases in medical comorbidities in adult patients with bipolar illness, and it is likely that inflammation could play a role in some of these medical conditions.
There is a large body of research showing that lithium is better than placebo and a variety of comparison drugs at preventing manic episodes in people with bipolar disorder. It has been less clear whether lithium is as effective in preventing depressions in bipolar patients. In a 2014 meta-analysis in the International Journal of Bipolar Disorders, Emanuel Severus and colleagues confirmed that lithium was more effective than placebo at preventing mood episodes overall and manic episodes. In a fixed effect statistical analysis, lithium was also better at preventing depressive episodes.
The portion of the meta-analysis comparing lithium to placebo included seven randomized controlled trials that included a total of 1,580 patients. Lithium was more likely than placebo to lead to patients dropping out of a study for reasons other than a mood episode, but patients who received lithium were more likely to complete their clinical trials.
Another part of the meta-analysis compared lithium to anticonvulsant drugs. Seven trials were included totaling 1,305 patients. Lithium was better than anticonvulsants at preventing manic episodes, but equally effective at preventing mood episodes overall and depressive episodes specifically. There was also no difference in patients dropping out of the trials or completing the trials.
The researchers concluded that lithium remains the most valuable treatment option for bipolar disorder, because no other drug has such consistent efficacy in preventing manias and depressions and mood episodes in general.
The incidence of irritable bowel disease has been increasing in recent years as obesity has increased. At a symposium at the 2014 meeting of the American Academy of Child and Adolescent Psychiatry, researcher Eva Szigethy discussed depression in inflammatory bowel disease, which most often involves Crohn’s disease or ulcerative colitis. These conditions are associated with increased levels of inflammatory markers such as interleukin 1 (IL-1), interleukin 6 (IL-6), and TNF alpha, and these in turn induce the acute phase reactive protein called c-reactive protein (CRP). The interleukins peak in the first 12 hours after an inflammatory challenge and CRP peaks at 48 hours and returns to normal at 120 hours. Il-6 is most closely associated with the somatic symptoms of inflammation, including depression, fatigue, loss of appetite, and decreased sleep, while TNF alpha is associated with non-somatic symptoms, such as irritability.
Szigethy found that in a randomized trial of cognitive behavior therapy versus supportive therapy in children with inflammatory bowel disease, inflammatory activity decreased significantly with cognitive behavioral therapy, and the therapy particularly helped the somatic symptoms of fatigue, sleep disorder, anhedonia (loss of interest in activities once enjoyed), appetite suppression, and mood dysregulation. In contrast, when antidepressants are given to those with inflammatory bowel disease, the drugs are not particularly helpful for these somatic symptoms. Inflammatory bowel diseases are treated with steroids in 21% of patients and with a genetically engineered drug called infliximab in 30%. Adding cognitive behavioral therapy to the regimen decreases CRP and red cell sedimentation rate, an associated measure of inflammation.
The discussant of the symposium on inflammation, Frank Lotrich, described how inflammation alters sleep, and this appeared to interact with genetic risk of illness. For example, those with certain genetic variations (the short SS allele of the serotonin transporter and the val-66-met allele of proBDNF) were most likely to experience sleep disturbance following treatment with interferon gamma, a treatment that fights the virus that causes Hepatitis C, creating inflammation in the process. Interferon gamma causes depression in about one-third of the patients who take it.
Lotrich pointed out that low levels of omega-3 fatty acids are associated with increased irritability and anger, and this is related to the presence of the A allele of TNF alpha. TNF alpha is also closely linked with irritability and anger, suggesting the possible benefits of omega-3 fatty acid supplementation to target irritability and anger more selectively. This would be consistent with the data of researcher Mary A. Fristad.
Il-6 is closely associated with the somatic symptoms of depression, particularly poor sleep, which is itself associated with increases in depression. This is consistent with inflammation being a marker of poor response to antidepressants; Lotrich noted that the selective serotonin reuptake inhibitors (SSRIs), which help depression, are far more effective against the non-somatic aspects of depression and less effective against low energy, decreased interest, and fatigue. However, extrapolating from the data on inflammatory bowel disease, cognitive behavioral therapy may be most helpful on these somatic symptoms.
New research suggests that the ratio of cortisol to C-reactive protein (CRP), a marker of inflammation, may be a biomarker of depression that affects men and women differently. In women, lower ratios of cortisol to CRP were associated with more severe depression symptoms, including poor quality sleep, sleep disturbances, and decreased extraversion. In men, higher ratios of cortisol to CRP were associated with more daytime disturbance and greater anxiety. The study by E.C. Suarez et al. was published in the journal Brain, Behavior, and Immunity.
Further work must be done to confirm whether low cortisol and high inflammation predicts depression in women, while the opposite (high cortisol and low inflammation) predicts depression in men.
Saffron, the expensive yellow spice derived from the plant Crocus sativus, was the subject of a recent meta-analysis in the journal Human Psychopharmacology. The meta-analysis included six studies of a total of 230 adult outpatients with major depressive disorder. In two of these studies, 30mg/day of saffron extract was as effective as 20mg/day of the antidepressant fluoxetine and 100mg/day imipramine for the treatment of mild to moderate depression had been in other studies.
Saffron is suggested to have anticancer, anti-inflammatory, antioxidant, and antiplatelet effects, and current clinical trials are exploring whether it could prevent and treat Alzheimer’s disease.
The current study was an effort to systematically analyze clinical trials on saffron to establish treatment parameters such as dosage in addition to safety information.
Deep brain stimulation is a treatment in which electrodes are implanted in the brain to treat movement or affective disorders. At the 2014 meeting of the International College of Neuropsychopharmacology, Thomas Schlaepfer reviewed the current status of studies of deep brain stimulation for depression. The bad news is that two double-blind randomized controlled studies are no longer recruiting patients because interim analysis failed to show a benefit to the deep brain stimulation over a sham stimulation. The studies targeted two of the most promising parts of the brain for deep brain stimulation—the subgenual anterior cingulate (important for motivation) and the anterior limb of the internal capsule (which contains nerve fibers going to and from the cerebral cortex), so their failure is a disappointment. However, Helen Mayberg, one of the lead researchers studying the subgenual anterior cingulate, will continue to study this target for deep brain stimulation.
The better news is that Schlaepfer repositioned the electrodes to target a site in the medial forebrain bundle nearer to the ventral tegmental area. After this shift he observed rapid onset of antidepressant response (within two days) in seven of the first eight patients studied, and these responses persisted over many months of follow up. This response was achieved at 2.8 microamps, a lower stimulation current than was used in other studies of deep brain stimulation.
Editor’s Note: Since patients started to feel better when they were still on the operating table, this may offer an opportunity to more rapidly assess effectiveness, do a double-blind study, and see if the findings can be replicated as another mode of achieving rapid-acting and long-lasting antidepressant effects in treatment-resistant patients. Intravenous ketamine has rapid-onset antidepressant effects, but its effects are short-lived.
To study depression in humans, researchers look to rodents to learn more about behavior. Rodents who are repeatedly defeated by more aggressive animals often begin to exhibit behavior that resembles depression. At the 2014 meeting of the International College of Neuropsychopharmacology (CINP), researcher Andre Der-Avakian reported that in a recent study, repeated experiences of social defeat led to depressive behavior in a subgroup of animals (which he calls susceptible), but not in others (which he calls resilient). Among many biological differences, the resilient animals showed increases in neurogenesis in the dentate gyrus of the hippocampus.
Chronic treatment of the susceptible animals with the selective serotonin reuptake inhibitor (SSRI) antidepressant fluoxetine or the tricyclic antidepressant desipramine, which both increase neurogenesis, also reversed the depressive behavior in about half of the animals. A single injection of the anesthetic ketamine (which has rapid-acting antidepressant effects in humans) reversed social avoidance behavior in about 25% of the animals. One depression-like symptom was anhedonia (loss of pleasure from previously enjoyed activities), which researchers measured by observing to what extent the animals engaged in intracranial self-stimulation, pressing a bar to stimulate the brain pleasurably. The effectiveness of the drugs in inducing resilient behavior was related to the degree of anhedonia seen in the animals. The drugs worked less well in the more anhedonic animals (those who gave up the intracranial stimulation more easily, indicating that they experienced less reward from it.)
Low levels of folate, also known as folic acid or vitamin B9, have been associated with depressive symptoms in the general population. A 2014 article by A.L. Sharpley et al. in the Journal of Affective Disorders explored whether folate has protective effects. Teens and young adults (ages 14–24) at high risk for mood disorders due to a family history of these illnesses were randomly assigned to receive either folate supplements (2.5 mg daily) or placebo for up to three months. While there were no significant differences in the percentage of young people in each group who went on to be diagnosed with a mood disorder, in the folate group there was a delayed onset of illness in those who went on to become unwell.
In a 2013 article in the journal European Psychiatry, in which researcher Valery V. Gafarov examined depression’s influence on cardiovascular health in Russia, an astonishing 55.2% of women aged 25–64 years in the study were diagnosed with depression. The study, in which 870 women in the city of Novosibirsk were surveyed over 16 years from 1995 to 2010, was part of a World Health Organization program called “MONICA-psychosocial.”
The researchers collected information on the incidence of myocardial infarction (heart attack), arterial hypertension, and stroke among the women. Over the 16 years of the study, 2.2% of the women had heart attacks and 5.1% had strokes. Women with depression were 2.53 times more likely to have a heart attack and 4.63 times more likely to have a stroke than women without depression.
Among women with average education levels, married women with depression were more likely to have heart attacks, hypertension, and strokes. Hypertension was more likely among women who worked as managers or light manual laborers.