New research shows that cocaine, defeat stress, the rapid-acting antidepressant ketamine, and learning and memory can change the size, shape, or number of spines on the dendrites of neurons. Dendrites conduct electrical impulses into the cell body from neighboring neurons.
Several researchers, including Peter Kalivas at the Medical University of South Carolina, have reported that cocaine increases the size of the spines on the dendrites of a certain kind of neurons (GABAergic medium spiny neurons) in the nucleus accumbens (the reward center in the brain). This occurs through a dopamine D1 selective mechanism. N-acetylcysteine, a drug that can be found in health food stores, decreases cocaine intake in animals and humans, and also normalizes the size of dendritic spines.
Depression in animals and humans is associated with decreases in Rac1, a protein in the dendritic spines on GABA neurons in the nucleus accumbens. Rac1 regulates actin and other molecules that alter the shape of the spines.
In an animal model of depression called defeat stress, rodents are stressed by repeatedly being placed in a larger animal’s territory. Their subsequent behavior mimics clinical depression. This kind of social defeat stress decreases Rac1 and causes spines to become thin and lose some function. Replacing Rac1 returns the spines to a more mature mushroom shape and reverses the depressive behavior of these socially defeated animals. Researcher Scott Russo has also found Rac1 deficits in the nucleus accumbens of depressed patients who committed suicide. Russo suggests that decreases in Rac1 are responsible for the manifestation of social avoidance and other depressive behaviors in the defeat stress animal model, and that finding ways to increase Rac1 in humans would be an important new target for antidepressant drug development.
Another animal model of depression called chronic intermittent stress (in which the animals are exposed to a series of unexpected stressors like sounds or mild shocks) also induces depression-like behavior and makes the dendritic spines thin and stubby. The drug ketamine, which can bring about antidepressant effects in humans in as short a time as 2 hours, rapidly reverses the depressive behavior in animals and converts the spines back to the larger, more mature mushroom-shape they typically have.
Learning and Extinction of Fear
Researcher Wenbiao Gan has reported that fear conditioning can change the number of dendritic spines. When animals hear a tone paired with an electrical shock, they begin to exhibit a fear response to the tone. In layer 5 of the prefrontal cortex, spines are eliminated when conditioned fear develops, and are reformed (near where the eliminated spines were) during extinction training, when animals hear the tones without receiving the shock and learn not to fear the tone. However, in the primary auditory cortex the changes are opposite: new spines are formed with learning, and spines are eliminated with extinction.
Editor’s Note: It appears that we have arrived at a new milestone in psychiatry. In the field of neurology, changes seen in the brains of patients with strokes or Alzheimer’s dementia have been considered “real” because cells were obviously lost or dead. Psychiatry, in comparison, has been considered a soft science because neuronal changes have been more difficult to see and illnesses were and still are called “mental.” Now that new technologies have made a deeper level of precision, observation, and analysis possible, we know that the brain’s 12 billion neurons and 4 times as many glial cells are exquisitely plastic–capable of biochemical and structural changes that can be reversed using appropriate therapeutic maneuvers.
The changes associated with abnormal behaviors, addictions, and even normal processes of learning and memory now have clearly been shown to correspond with the size, shape, and biochemistry of dendritic spines. These subtle, reproducible changes in the brain and body are amenable to therapeutic intervention, and are now even more demanding of sophisticated medical attention.
We have previously summarized studies on ketamine, which when given intravenously can bring about rapid-onset antidepressant effects. Ketamine is a full antagonist (or a blocker) of the glutamate NMDA receptors. Another drug currently in development may work in a related way.
At a recent scientific meeting, researcher Sheldon Preskorn showed that the compound GLYX-13, a partial agonist at the glycine binding site of the NMDA receptor (meaning it allows partial function of the glycine receptors that aid NMDA receptor function), exerts rapid antidepressant effects like the full antagonist ketamine when administered intravenously compared to placebo. GLYX-13 allows about 25% of the receptor activity of the full agonists glycine or D-serine, and thus might result in a 75% inhibition of NMDA receptor function.
GLYX-13 did not induce any psychotomimetic effects (like delusion or delirium), which are possible with the full NMDA antagonist ketamine. The effects of GLYX-13 appeared within 24 hours, lasted at least 6 days, but were gone by day 14.
Editor’s Note: Long-term effectiveness of ketamine for treatment of depression is unclear, but in addition to its potential psychotomimetic effects, it can also be abused. Whether GLYX-13 may be easier to use, longer-lasting, or safer for longer-term clinical effectiveness remains a key question.
We’ve written before about the rapid-onset antidepressant effects of ketamine, an anesthetic that is used in human and veterinary medicine. At lower doses, intravenous (IV) ketamine can induce antidepressant effects in both unipolar and bipolar depressed patients. When doses of 0.5mg/kg are infused over a period of 40 minutes, antidepressant effects appear within two hours but are short-lived, typically lasting only three to five days. Results have been consistent across studies at Yale University, the Icahn School of Medicine at Mount Sinai, and the National Institute of Mental Health. So far, clinical use has been limited by the short duration of the effects and the required presence of an anesthesiologist, which can be prohibitively expensive for many patients.
In a cover story in the January 2013 issue of Psychiatric Times, Arline Kaplan reviewed new findings about ketamine. The drug is a high-affinity, noncompetitive NMDA-glutamate receptor antagonist. It is not yet FDA-approved for use in depression.
According to a recent article by Murrough and Charney, response rates to ketamine are around 54% and the drug “appears to be effective at reducing the range of depressive symptoms, including sadness, anhedonia [the loss of ability to experience pleasure], low energy, impaired concentration, negative cognitions, and suicidal ideation.”
David Feifel, Director of the Neuropsychiatry and Behavioral Medicine Program at the University of California at San Diego (UCSD), instituted a program there in which patients can receive treatment with ketamine for clinical purposes (rather than for research) after signing detailed informed consent forms and being warned that the treatment is not yet approved for depression and that its effects may be temporary. The UCSD Medical Center’s Pharmacy and Therapeutics Committee, with the support of the anesthesiology department, agreed that nurses may administer the ketamine in an outpatient setting, making the procedure more affordable.
There is still the question of how to make ketamine’s effects last. Read more
Physical activity and light to moderate drinking (as is often associated with the Mediterranean diet) are recommended as ways to reduce risk for heart disease and type 2 diabetes. New research shows that among healthy people, symptoms of depression can counteract the anti-inflammatory benefits of both exercise and light to moderate alcohol consumption.
C-reactive protein (CRP) is a cardiometabolic risk marker. High measures of CRP are a sign of inflammation. Leisure-time physical activity and light to moderate alcohol intake (defined as about half a drink per day for women and one drink per day for men) are associated with lower levels of CRP. Depression is associated with higher levels.
A study by Edward C. Suarez et al. published recently in the journal Brain, Behavior, and Immunity examined 222 nonsmoking men and women aged 18-65 years. These participants were physically healthy and had no history or diagnosis of psychiatric conditions. Participants recorded the amount of alcohol they consumed and the amount of physical activity in which they participated. CRP levels in their fasting blood samples were measured, and they also completed an inventory of depressive symptoms.
Those people who were physically active had lower levels of CRP, but the 4.5% of participants with depressive symptoms did not see any anti-inflammatory benefits from physical activity. Similarly, light to moderate drinking was associated with lower levels of CRP only in men who were not depressed.
Depression did not seem to affect other markers of physical health in this study, such as levels of triglycerides or cholesterol.
Editor’s Note: This study suggests that treating depressive symptoms should be a part of any plan to reduce cardiovascular risk. It seems that depression has effects that go beyond psychological distress and may prevent patients from reaping the benefits of their healthy behaviors. The effect of depression in preventing heart healthy changes in CRP could be one of many factors mediating the high levels of cardiovascular risk in depression. People with depression are twice as likely to have a heart attack than those without depression.
Research has connected cardiovascular fitness with depression risk and treatment. A Swedish study published last year in the British Journal of Psychiatry examined records of men conscripted into the military at age 18 and compared their cardiovascular fitness at the time with hospital records from later decades. Low cardiovascular fitness at the time of conscription was associated with increased risk for serious depression.
Editor’s Note: This study provides more evidence that exercise, which increases cardiovascular fitness and decreases many of the elements of the metabolic syndrome, is good for cardiovascular and neuropsychological health, including mood stability. It is noteworthy that exercise also increases both brain-derived neurotrophic factor or BDNF (important for neural development and long-term memory) and neurogenesis (in animals), effects shared by almost all treatments with antidepressant properties. Making exercise a routine part of a regimen aimed at medical and psychiatric health is a great idea.
Many patients with depression require two or more treatments in order to achieve remission. In a 2011 study by Trivedi et al. published in the Journal of Clinical Psychiatry, patients with major depressive disorder who had not responded adequately to selective serotonin reuptake inhibitor (SSRI) antidepressants improved when an exercise regimen was added to their regular treatment.
The patients, aged 18-70 years old, were all sedentary at the start of the trial. They were randomized to one of two exercise regimens: a high dose regimen (16 kcal/kg per week, equivalent to walking at about 4 mph for 210 minutes per week) or the low dose (4 kcal/kg per week, equivalent to walking at 3 mph for about 75 minutes per week). Both groups improved significantly by the end of the study. Remission rates (adjusted for differences between groups) were 28.3% for the high dose group and 15.5% for the low dose group.
The rates of improvement with exercise were similar or better to those commonly seen with other augmenting agents such as lithium, T3, buspirone, and atypical antipsychotics, but without side effects and other inconveniences such as blood monitoring.
Other studies have indicated that exercise by itself and in combination with other treatments has efficacy in depression. Exercise can change serotonin and norepinephrine function and can increase brain-derived neurotrophic factor (BDNF), a, and neurogenesis in the hippocampus.
The researchers looked for moderating variables that may have affected the outcomes of various participants. Men, regardless of family history of mental illness, had better remission rates in the high dose group. Women without a family history of mental illness also improved more in the high dose group, while women with a family history of mental illness improved more in the low dose group, though this finding was statistically nonsignificant.
While the researchers observed that those in the high-dose group did exercise more than those in the low-dose group, participants in the high-dose group had more difficulty sticking to their exercise regimen. It may be that even though high doses of exercise offer slightly higher rates of remission, lower doses may be more effective clinically if patients can stick to the low-dose regimen better.
Synthetic marijuana, otherwise known as spice, skank, or K2, is not only vastly more potent than the tetrahydrocannabinol (THC) in marijuana plants, but it also lacks cannabidiol (CBD), the calming, antipsychotic substance also present in the plants. This makes spice much more likely to induce major psychiatric effects.
New evidence links use of spice during pregnancy to a tragic birth defect, anencephaly, or absence of the cerebral cortex. It can also lead to the later development of attention-deficit hyperactivity disorder, learning disabilities, memory impairment, depression, and aggression.
Effects of THC on gestation may occur as early as two weeks after conception, meaning by the time a woman realizes she is pregnant, the fetus may have been harmed by exposure to the drug.
Other new finding associate use of spice with acute coronary syndrome and the kind of acute kidney injury that can lead to the organ shutting down.
Editor’s Note: It has now been found that synthetic marijuana, or spice, can lead to psychosis, delirium, acute coronary syndrome (heart attack) in young people, and now kidney dysfunction, in addition to causing birth defects if used by pregnant women. Not only is spice made up of more potent THC without the calming effects of CBD, but it is often laced with unknown contaminants, which are likely the cause of the heart and kidney damage.
Smoking regular marijuana is bad enough—it doubles the risk of psychosis and may precipitate the onset of schizophrenia. It may also cause long-lasting effects on cognitive function. Since many states are legalizing marijuana, it is important to know the risks. In any case the risks are much more serious with the synthetic product, and synthetic marijuana should be avoided at all costs.
The risk of having a depressive episode during pregnancy compared to afterward have not often been studied. A 2011 review article by Viguera et al. in the American Journal of Psychiatry compared rates of affective episodes among women with bipolar I and II disorders and recurrent major depressive disorder, both during pregnancy and the postpartum period. Risks were higher for women with bipolar disorder.
Among women with bipolar disorder, 23% experienced mood episodes during the pregnancy, while 52% had an episode in the months after giving birth. Among women with unipolar depression, 4.6% had a mood episode during pregnancy, while 30% did during the postpartum period, which is about double the risk seen in the general population. Depression was the most common type of morbidity the women experienced before and after giving birth.
Risk factors associated with mood episodes during pregnancy included (in descending order): younger age at illness onset, previous postpartum episodes, fewer years of illness, bipolar disorder, fewer children, and not being married. Risk factors associated with postpartum episodes included: younger age at illness onset, illness during pregnancy, bipolar disorder, fewer children, and more education.
Editor’s Note: The risk of postpartum depression increases from 15% in the general population, to 30% among women with unipolar disorder, to 50% in women with bipolar disorder. Special precautions should be taken to monitor and treat depression during and after pregnancy, in all women but particularly in those with a prior history of unipolar or bipolar disorder.
Atypical depression is characterized by overeating and oversleeping compared to the loss of appetite and early morning awakening associated with melancholic depression. A recent placebo-controlled study of chromium picolinate (600?g of elemental chromium) for atypical depression was not initially successful, but researcher Maurizio Fava and colleagues re-analyzed the data using a “population-enrichment strategy” to control for excessively high or low placebo response rates. Their analysis looked more positive than the initial analysis, but remained non-significant, possibly due to the small size of the study. However, the positive trend they saw made the researchers think that chromium picolinate is still worthy of future study.
Editor’s Note: Chromium picolinate had previously been shown (in one study by John Docherty et al.) to have positive effects in reducing carbohydrate craving when compared to placebo. If it only did that, it would still be useful for those struggling with overeating, even if it failed to improve other aspects of atypical depression.
Much has been written about the use of selective serotonin reuptake inhibitor (SSRI) antidepressants during pregnancy. In a review of 920,620 births in Denmark (1995 to 2008) that Jimenez-Solem published this year in the American Journal of Psychiatry, no link was found between any of the SSRIs used in any trimester and risk of stillbirth or neonatal mortality. The only exception was a possible association of three-trimester exposure to citalopram and neonatal mortality.
Editor’s Note: These new data may be of importance to women considering antidepressant continuation during pregnancy when there is a high risk for a depressive relapse. A maternal depressive episode (like other stressors such as anxiety or experiencing an earthquake) during pregnancy does convey adverse effects to the child, so appropriate evaluation of the risk/benefit ratio or staying on an antidepressant through a pregnancy is important.