Smoking, alcohol use, obesity, and diabetes aren’t just harmful to the body. They may actually lead to dementia.
Behavioral risk factors for cardiovascular disease like those listed above have been linked to reduced volume in the brain as a whole and several brain regions, including the hippocampus, precuneous, and posterior cingulate cortex. A 2015 study by researcher Kevin King and colleagues found that these reduced brain volumes are early indicators of cognitive decline.
King and colleagues analyzed data on 1,629 participants in the long-term Dallas Heart Study. Their cardiovascular risk factors were assessed when they began the study, and their brain volume and cognitive function were measured seven years later.
Alcohol use and diabetes were associated with lower total brain volumes, while smoking and obesity were linked to low volumes in the posterior cingulate cortex.
Low hippocampal volume was linked to past alcohol use and smoking, while lower precuneous volume was linked to alcohol use, obesity, and blood glucose levels.King and colleagues suggested that subtle differences in brain volumes in midlife are the first sign of developing dementia in participants who were still younger than 50 years of age.
The couch potato lifestyle common in the US may have consequences later, in the form of deficits in memory, executive functioning (including planning and execution) and processing speed.
At the 2015 Alzheimer’s Association International Conference, researcher Kristine Yaffe and colleagues reported that low levels of physical activity and high rates of television viewing in young adulthood may reduce cognitive capabilities in midlife.
The Centers for Disease Control report that less than 50% of adults aged 18–64 get the recommended minimum of physical activity each week. The guidelines recommend at least 150 minutes of moderate intensity aerobic activity (such as walking briskly) and two or more days of muscle-strengthening activities that work all major muscle groups.
Yaffe says that physical activity can protect against cognitive decline or dementia later on.
Participants in the long-term study who reported burning fewer than 300 calories per 50-minute session three times per week during two-thirds of their followup visits had worse cognition at year 25 than those participants who were more active. Those who watched more than four hours of television per day also had reduced cognition in midlife.
Yaffe stresses that exercising regularly is not just important in keeping weight down and protecting the heart, but also in protecting the brain. Regular physical activity may even prevent illnesses such as Alzheimer’s disease.
Depression and Bipolar Disorder in Adolescence Linked to Early-Onset Cardiovascular Disease and Hardening of the Arteries
The link between mood disorders and cardiovascular illnesses has been clear for some time. Now there is evidence that this link begins early in life. In 2015, the American Heart Association issued a statement that adolescents with major depressive disorder and bipolar disorder are at increased risk for both accelerated atherosclerosis (narrowing and hardening of the arteries) and early-onset cardiovascular disease.
In the statement, the American Heart Association recommended that major depressive disorder and bipolar disorder be classified as “tier II” conditions (which also include HIV and chronic inflammatory disease) that confer a moderate risk of disease.
Until recently, it had been assumed that the increased risk of cardiovascular disease among people with depression or bipolar disorder was a result of behaviors linked to these illnesses, such as higher rates of smoking, obesity, or diabetes, which increases heart disease. Some psychiatric medication can also bring about risk factors for cardiovascular problems. It turns out that these types of factors could not fully explain the increased risk of atherosclerosis and cardiovascular disease among people who had depression or bipolar disorder in their teens.
It is not clear why depression and bipolar disorder make cardiovascular illness more likely, though it may be due to blood vessel damage resulting from inflammation or oxidative stress.
The American Heart Association recommends that pediatricians and cardiologists pay particular attention to this link by identifying and treating mental illness as early as possible and by making sure that their colleagues understand the role of mental illnesses in cardiovascular risk.
Professional football players face repeated mild traumatic brain injuries throughout their careers, and may face a variety of brain impairments, from depression to dementia, as a result.
A recent study by researcher Jennifer Coughlin and colleagues clarified how these impairments may be caused by repeated brain impacts. The researchers used positron emission tomography (PET) scans to observe the volume of translocator protein, a marker of brain injury and repair, in the brains of seven active or recently retired National Football League (NFL) players. Compared to healthy, athletic volunteers who were age-matched to the NFL players, the NFL players showed greater volume of translocator protein in several brain regions, including the left and right thalamus, the left and right temporal poles, and the brainstem.
It is not yet clear whether the increased volume of translocator protein is a sign of the brain’s attempts to repair itself, or whether it shows deterioration toward chronic traumatic encephalopathy. Translocator protein is also considered a marker of microglial activation, which occurs with inflammation.
High levels of translocator protein have also been seen in patients with depression and schizophrenia.
Low levels of vitamin D have been linked to schizophrenia in several studies. In one, infants with low vitamin D were more likely to develop schizophrenia in adulthood, but supplementation reduced this risk. A 2015 article by Venkataram Shivakumar and colleagues in the journal Psychiatry Research: Neuroimaging found that among patients with schizophrenia who were not currently taking (or in some cases, had never taken) antipsychotic medication, low levels of vitamin D were linked to smaller gray matter volume in the right hippocampus, an area involved in schizophrenia.
Vitamin D has neuroprotective effects and is important to normal brain development and function. Vitamin D is essential to the production of brain-derived neurotrophic factor (BDNF), a protein that is important for learning and memory, and vitamin D also reduces oxidative stress. BDNF deficiency and oxidative stress have both been linked to schizophrenia, and they both can cause abnormalities in the hippocampus.
Telomeres are repeated DNA sequences that sit at the end of chromosomes and protect them during cell replication. Shorter telomeres are associated with aging and an increase in multiple medical and psychiatric disorders, while some healthy behaviors including exercising, eating healthy, meditating, and avoiding smoking can help maintain telomere length. Lithium treatment also increases telomere length.
Recent research by Mateus Levandowski and colleagues found that people who were dependent on crack cocaine had shorter telomeres than elderly women without psychiatric illnesses, particularly if the crack cocaine users had also experienced stress early in life, such as maltreatment or neglect.
Since short telomeres are associated with a variety of medical and psychiatric problems and premature aging, the combined effects of drug use and early life stressors are likely to have an adverse impact on people who have experienced both.
Stress is a risk factor for depression and other mental health disorders. Researchers are currently working to clarify how stress leads to depression, anxiety, and post-traumatic stress disorder, and why trauma early in life has lasting consequences.
Two recent studies in mice examined whether just witnessing a stressful event leads to depression-like behaviors. In one, adult female mice watched a male mouse as it was repeatedly attacked by a larger mouse. After ten days of this, the female mice were socially withdrawn, had lost interest in drinking sucrose, and gave up more easily during a physical challenge. They also lost weight and showed higher levels of the stress hormone corticosterone in their blood. The researchers, led by Sergio Iniguez, believe their study clarifies how witnessing traumatic events can lead to stress-induced mood disorders.
In the other study, by Carlos Bolanos-Guzman, adolescent male mice witnessed another mouse being attacked. Both the mice that went through the physical stress of being attacked and the mice that went through the emotional stress of watching the attacks occur showed similar depressive behaviors to the mice in the previous study—social withdrawal, loss of interest in sucrose, decreased food intake and exploration of the environment, and decreased motivation in physical challenges. These behaviors persisted into adulthood. Both groups of mice also had increased levels of corticosterone and reduced expression of a particular protein in the ventral tegmental area, a part of the brain linked to stress response. Bolanos-Guzman suggests that both physical and emotional stress have lifelong consequences in mice.
The studies were presented at a scientific meeting in December.
Many psychiatric illnesses, including bipolar disorder, schizophrenia, autism, attention deficit hyperactivity disorder (ADHD), and anxiety disorders may stem from abnormalities in brain development that begin before birth. Researchers are trying to determine whether dietary supplements taken by pregnant mothers or infants can reduce the risk of such illnesses. At a recent scientific meeting, researcher Randal Ross and colleagues reported that compared to placebo, choline supplements reduced problems with a brain process called sensory gating in one-month-old infants and also improved the children’s attention span and social skills at age 3.
Sensory gating is the process by which the brain filters out unimportant information, to avoid flooding higher cortical centers with irrelevant stimuli. Deficits in the way the brain inhibits response to this type of irrelevant information are associated with mental illnesses such as schizophrenia.
In Ross’s study, healthy pregnant mothers received either a placebo or 6300 mg of choline, a nutrient found in liver, egg yolks, and meat. After delivery, the infants also received 700 mg of supplemental choline per day. In children who carried CHRNA7, a risk gene for schizophrenia discovered by Ross’s colleague Robert Freedman, choline reversed the associated risk of sensory gating problems and normalized their behavior at age 3.
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.