Quetiapine Reduced Childhood Mania, Especially in Those with Thicker Frontal Temporal Regions
In a symposium at the 2019 meeting of the American Academy of Child and Adolescent Psychiatry, researcher Melissa P. Delbello reported that six weeks of treatment with either lithium or quetiapine was effective in childhood mania, but quetiapine had a higher response rate of 71% versus 46% for lithium. Delbello found two types of structural changes on functional magnetic resonance imaging (fMRI). Some children had thicker frontal temporal regions, while others had thinning in these areas. The first group of patients had a 100% response to quetiapine, but only 53% of the second group responded to quetiapine.
In contrast, other researchers have found lithium superior to quetiapine. Vivian Kafantaris showed that patients who respond well to lithium show improvements in white matter abnormalities. Michael Berk and colleagues found that a year on lithium was superior to quetiapine on all measures including cognition and brain imaging in patients having their first episode of mania.
Inflammation Predicts Lower Frontal and Temporal White Matter Volumes in Early-Stage Bipolar Disorder
At the 2019 meeting of the International Society for Bipolar Disorders, researcher David Bond found that seven inflammatory cytokines predicted lower white matter volumes in the left frontal and bilateral temporal lobes, as well as in the cingulate and inferior frontal gyri. Cytokines are secreted by some immune cells and send signals that can produce an effect in other cells.
Bond noted that greater inflammation did not predict lower parietal or occipital white matter volumes, suggesting that inflammation had a greater effect on white matter volume in those parts of the brain most closely linked to mood disorders.
Lithium Reverses Thinning of the Cortex That Occurs in Bipolar Disorder
In a 2018 article in the journal Molecular Psychiatry, researcher Derrek P. Hibar reported findings from the largest study to date of cortical gray matter thickness. Researchers in the ENIGMA Bipolar Disorder Working Group, which comprises 28 international research groups, contributed brain magnetic resonance imaging (MRI) from 1837 adults with bipolar disorder and 2582 healthy control participants.
Hibar and colleagues in the working group found that in adults with bipolar disorder, cortical gray matter was thinner in the frontal, temporal, and parietal regions of both brain hemispheres. They also found that bipolar disorder had the strongest effect on three regions in the left hemisphere: the pars opercularis, the fusiform gyrus, and the rostral middle frontal cortex.
Those who had had bipolar disorder longer (after accounting for age at the time of the MRI) had less cortical thickness in the frontal, medial parietal, and occipital regions.
A history of psychosis was associated with reduced surface area.
The researchers reported the effects of various drug treatment types on cortical thickness and surface area. In adults and adolescents, lithium was associated with improvements in cortical thickness, and the researchers hypothesized that lithium’s protective effect on gray matter was responsible for this finding. Antipsychotics were associated with decreased cortical thickness.
In people taking anticonvulsant treatments, the thinnest parts of the cortex were the areas responsibly for visual processing. Visual deficits are sometimes reported in people taking anticonvulsive treatments.
Lithium Reverses Some White Matter Abnormalities in Youth with Bipolar Disorder
Multiple groups of researchers have reported the presence of white matter tract abnormalities in patients with bipolar disorder. Some of these abnormalities correlate with the degree of cognitive dysfunction in these patients. These white matter tract abnormalities, which are measured with diffusion tensor imaging (DTI), are widespread and can appear as early as childhood in people with bipolar disorder. Researcher Vivian Kafantaris mentioned at the 2019 meeting of the International Society for Bipolar Disorders that lithium treatment in children and adolescents normalizes these alterations, as described in an article she and her colleagues published in the journal Bipolar Disorders in 2017.
Editor’s Note: This is another reason to consider the use of lithium in children with bipolar disorder. Lithium treatment may help normalize some of the earliest signs of neuropathology in the illness.
Inflammation Associated With Duration of Untreated Unipolar Depression
Researcher Sophia Attwells and colleagues reported at a 2018 scientific meeting that the longer the time that a patient went without treatment for depression, the more inflammation they exhibited on positron emission tomography (PET) scans. Attwells and colleagues used the PET scans to assess the total distribution volume of TSPO, which is a marker of brain microglial activation, a form of inflammation.
Strikingly, in participants who had untreated major depressive disorder for 10 years or longer, TSPO distribution volume was 29–33% greater in the prefrontal cortex, anterior cingulate cortex, and insula than in participants who were untreated for 9 years or less. TSPO distribution volume was 31–39% greater in these three important regions of gray matter in participants with long durations of untreated major depressive disorder than in healthy control participants.
Editor’s Note: In schizophrenia, the duration of untreated interval (DUI) is associated with a poor prognosis, but not with inflammation. Researcher Yvette Sheline has also reported that less time on antidepressants compared to more time treated with them was associated with greater hippocampal volume loss with aging in patients with major depression.
Given Attwells and colleagues’ remarkable finding about the adverse effects of the DUI in depression, including inflammation and brain volume loss, and other findings that associate more episodes with poorer functioning, cognition, and treatment responsiveness, physicians and patients should think hard about committing to long-term antidepressant treatment to prevent episodes, beginning early in the course of illness.
This editor (Robert M. Post) would propose that if a second depressive episode occurs after a first depression that responded well to treatment, this would be an appropriate time to start antidepressant prophylaxis. Most guidelines suggest that prophylaxis be started after a third episode, but these recommendations generally do not account for newer data on the pernicious effects of experiencing repeated depressive episodes. In addition to causing dysfunction and disability, going through four depressive episodes doubles the risk of dementia in old age, and this risk increases further with each successive episode, according to researcher Lars Kessing.
Having too many depressions is bad for the brain. In Kessing’s studies, two episodes of unipolar or bipolar depression did not increase the risk of dementia compared to the general population, while four depressions did. One could compare the effects of repeated depressions on the brain to the effects of heart attacks on the heart muscle. A heart might still function well after one or even two heart attacks, but the chances of significant loss of function and the risk of congestive heart failure increase as a function of the number of heart attacks. After even one heart attack, most patients change their lifestyle and/or go on prophylactic medications to reduce risk factors such as elevated blood pressure, cholesterol, triglycerides, weight, blood sugar, and smoking. The benefits of reducing heart attacks are a no brainer. Trying to prevent recurrent depression with pharmacotherapy and adjunctive psychotherapy after a second depressive episode should be a no brainer too.
In addition, if antidepressants are not effective enough in preventing depressions, lithium is an option, even in unipolar depression, for preventing both episodes and suicide. The evidence of efficacy in both instances is very strong according to an article by Mohammed T. Abou-Saleh in the International Journal of Bipolar Disorders in 2017. The renowned psychiatrist Jules Angst’s recommendation as to when to start lithium treatment was that if a patient had had one episode or more in the previous five years in addition to the present episode, then they were likely to have two further episodes in the following five years, and lithium prophylaxis would be recommended.
Risk Gene for Bipolar Disorder Implicated in Depressed Behaviors and Abnormal Firing of GABA Neurons
At a 2018 scientific meeting and in a 2017 article in the journal PNAS, researcher Shanshan Zhu and colleagues reported that mice genetically engineered to lack the protein Ankyrin-G in certain neurons showed increases in depression- and mania-like behavior after being exposed to defeat stress (by repeatedly being placed in physical proximity to a larger, more aggressive mouse), which is often used to model human depression.
The researchers targeted the gene ANK3, which is responsible for the production of Ankyrin-G, and has been linked to bipolar disorder in genome-wide association studies. By manipulating the gene, they could eliminate Ankyrin-G in pyramidal neurons in the forebrain, a region relevant to many psychiatric disorders. Pyramidal neurons perform key brain functions, sending nerve pulses that lead to movement and cognition.
The missing Ankyrin-G affected sodium channels (which allow for the flow of sodium ions in and out of cells) and potassium channels. The neurochemical GABA (which typically inhibits nerve impulses) was also dysregulated, resulting in the kind of disinhibition seen in psychosis. Mice showed dramatic behavioral changes ranging from hyperactivity to depression-like behavior (e.g. giving up in a forced swimming test). The hyperactivity decreased when the mice were given treatments for human mania, lithium or valproic acid.
While mutations in the ANK3 gene may disturb sodium channels, another gene linked to depression and bipolar disorder, CACNA1C, affects calcium channels.
In a related study by researcher Rene Caballero-Florán and colleagues that was also presented at the meeting, mice were genetically engineered in such a way that interactions between Ankyrin-G and GABA Type A Receptor-Associated Protein (GABARAP) were disrupted, leading to deficits in inhibitory signaling. These deficits were partially corrected when the mice were treated with lithium.
The study by Caballero-Florán and colleagues used mice with a mutation known as W1989R in the ANK3 gene. Through a program that examines the genes of people with bipolar disorder, the researchers also identified a family with this genetic mutation, including a patient with type I bipolar disorder with recurrent mania and depression who has responded well to lithium treatment.
White Matter Abnormalities in Obesity
Researcher Ramiro Reckziegel and colleagues reported at a recent scientific meeting that white matter is abnormal in obese adults with bipolar disorder. In a 2018 article in the journal Schizophrenia Bulletin, Reckziegel reported that body mass index (BMI) was associated with reduced fractional anisotropy, a measure of brain fiber integrity, in the cingulate gyrus in patients with bipolar disorder. This finding implies that obesity may play a role in white matter microstructure damage in the limbic system.
White Matter Abnormalities Linked to Irritability in Both Bipolar Disorder and DMDD
At a 2018 scientific meeting, researcher Julia Linke of the National Institute of Mental Health reported that there were white matter tract abnormalities in young people who had irritability associated with either bipolar disorder or disruptive mood dysregulation disorder (DMDD). Thus, while these two disorders differ in terms of diagnosis, presentation, and family history, they seem to have this neurobiological abnormality in common.
Scientific Mechanisms of Rapid-Acting Antidepressants
A pyramidal cell (Photo by Bob Jacobs, Laboratory of Quantitative Neuromorphology Department of Psychology Colorado College)
At a recent symposium, researcher Francis McMahon provided electrophysiological evidence that several different types of rapid-acting antidepressants—low-dose ketamine, scopolamine, and rapastinel (a partial agonist of the neurotransmitter NMDA)—act by decreasing the inhibitory effects of GABAergic interneurons on excitatory neurons called pyramidal cells, thus increasing synaptic firing.
Researcher Ronald Duman further dissected these effects, showing that ketamine and its active metabolite norketamine reduce the steady firing rate of GABA interneurons by blocking NMDA receptors, while the partial agonist rapastinel acts on the glutamate neurons directly, and both increase the effects of a type of glutamate receptors known as AMPA. These effects were demonstrated using a virus to selectively knock out GluN2B glutamate receptor subunits in either GABA interneurons or glutamate neurons.
Increasing AMPA activity increases synapse number and function and also increases network connectivity, which can reverse the effects of stress. Duman and colleagues further showed that when light is used to modulate pyramidal cells (a process called optogenetic stimulation) in the medial prefrontal cortex, different effects could be produced. Stimulating medial prefrontal cortex cells that contained dopamine D1 receptors, but not D2 receptors, produced rapid and sustained antidepressant effects. Conversely, inhibiting these neurons blocked the antidepressant effects of ketamine. Stimulating the terminals of these D1-containing neurons in the basolateral nucleus of the amygdala was sufficient to reproduce the antidepressant effects. These data suggest that stimulation of glutamate D1 pyramidal neurons from the medial prefrontal cortex to the basolateral nucleus of the amygdala is both necessary and sufficient to produce the antidepressant effects seen with ketamine treatment.
Researcher Hailan Hu reported that NMDA glutamate receptors drive the burst firing of lateral habenula (LHb) neurons, which make up the depressogenic or “anti-reward center” of the brain and appear to mediate anhedonic behavior (loss of interest or enjoyment) in animal models of depression. Ketamine blocks the burst firing of the LHb neurons, which disinhibits monoamine reward centers, enabling ketamine’s rapid-onset antidepressant effects. This may occur because inhibitory metabotropic glutamate receptors (mGluR-2) are activated, decreasing the release of glutamate.
MGluR-2 may also help explain the antidepressant effects of acetyl-L-carnitine supplements. L-carnitine is an amino acid that is low in the blood of depressed patients. The supplement acetyl-L-carnitine (ACL) activates the DNA promoter for mGluR-2, increasing its production and thus decreasing excess glutamate release. The acetyl group of the ACL binds to the DNA promoter for mGluR-2, thus this process seems to be epigenetic. Epigenetic mechanisms affect the structure of DNA and can be passed on to offspring even though they are not encoded in the DNA’s genetic sequence.
Inflammation and Depression: Treatment Implications
Vladimir Maletic of the University of South Carolina School of Medicine Greenville gave a plenary talk at the 2018 meeting of the North Carolina Psychiatric Association that described a variety of ways that inflammation can drive depression.
Maletic explained that stress can increase neurotransmitters that activate brain macrophages, increase NFkB (a protein that controls DNA transcription and cell survival), and increase brain inflammation, evidenced by elevated levels of the inflammatory markers IL-1b, IL-6, TNF-alpha, and C-reactive protein (CRP). These signs of inflammation are associated with changes in brain function and connectivity that are consistent with depression, fatigue, and cognitive slowing.
Inflammation measured outside of the brain and spinal cord is associated with increased activity of the insula (a key brain sensor and modulator of emotions), disconnection between the prefrontal cortex and the reward circuits in the nucleus accumbens, and decreased function and structural changes to the hippocampus (critical for memory).
Maletic also explained that inflammation changes the way the amino acid tryptophan is metabolized. Normally tryptophan is converted into kyneurenic acid, which prevents excitotoxicity and has anticonvulsant effects. Stress can lead to tryptophan being metabolized instead into quinolinic acid, which is neurotoxic and has been linked to certain psychiatric disorders and neurodegenerative processes. This in turn impairs synaptic functioning, including increasing glutamate and decreasing brain-derived neurotrophic factor (BDNF), impairing a type of glia called oligodendroglia (which produce myelin), and the formation of new neural connections.
These findings have several important implications for treatment. Increases in inflammation have been linked to the atypical type of depression characterized by increased appetite, weight gain, and increased sleep rather than the more classic presentation of depression that includes loss of appetite, weight loss and insomnia. Thus, weight gain, waist circumference, and body mass index (BMI) are correlated with inflammation and can signal a poor response to medications (including the rapid-acting antidepressant ketamine and some other antidepressants). If someone with unipolar depression has high levels of CRP, they tend to have a poorer response to selective serotonin reuptake inhibitor (SSRI) antidepressants, and may respond better to the noradrenergic tricyclic antidepressant nortryptyline, the serotonin and norepinephrine reuptake inhibitors (SNRIs), and the dopamine active antidepressant bupropion.
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