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Why mental health disorders are becoming more common


Issue of mental illness

A new study has concluded that living alone is linked to common mental disorders. The authors have also identified the main driver of this worrying relationship.

Some common mental disorders (CMDs) include mood disorders, anxiety, and substance use disorders.

According to some studies, almost one-third of people will experience a CMD in their lifetime.


These conditions can have a significant impact on the individual, of course, but due to their high prevalence, they also affect society at large. Due to the widespread influence of CMDs, scientists are keen to understand the full range of risk factors that feed into mental health.

In recent years, scientists have investigated whether living alone might be one such risk factor.

A new study, the results of which now appear in the journal PLOS ONE, takes a fresh look at this question. The study authors conclude that there is a link between living alone and CMDs. They also find that it affects all age groups and sexes, and that primarily, loneliness is the driver.

The number of people living alone is steadily growing throughout much of the Western world; this is due to a number of reasons, including the aging population, people tending to get married at an older age, and increased divorce rates.

Researchers have already looked at the relationship between CMDs and living alone, but most have focused on older adults, so their findings may not apply to other age groups.

A recent study has confirmed that loneliness is linked to a higher risk of developing dementia.

Also, a Massachusetts General Hospital (MGH), United States, study has found evidence that children under three years old are most the vulnerable to the effects of adversity – experiences including poverty, family and financial instability, and abuse – on their epigenetic profiles, chemical tags that alter gene expression and may have consequences for future mental health. Their report appearing in the May 15 issue of Biological Psychiatry, which has been published online, finds that the timing of adverse experiences has more powerful effects than the number of such experiences or whether they took place recently.


“One of the major unanswered questions in child psychiatry has been ‘How do the stressors children experience in the world make them more vulnerable to mental health problems in the future?’,” says Erin Dunn, ScD, MPH, of the Psychiatric and Neurodevelopmental Genetics Unit in the MGH Center for Genomic Medicine, corresponding author of the report.

“These findings suggest that the first three years of life may be an especially important period for shaping biological processes that ultimately give rise to mental health conditions. If these results are replicated, they imply that prioritizing policies and interventions to children who experienced adversity during those years may help reduce the long-term risk for problems like depression.”

Also, a survey of thousands of people suggests that mystical experiences positively affect a person’s mental health, regardless of whether they are naturally occurring or a result of psychedelic drugs.

Religion may have a wide range of health benefits, research suggests.

For instance, a study that appeared last year found that religious believers tend to live four years longer, on average, while another study found that attending religious ceremonies slashes the risk of premature death among seniors.

Emerging research is also looking into the mental health benefits of various psychedelic substances.

For example, several studies have shown that psilocybin — the psychoactive compound in so-called magic mushrooms — has the potential to treat severe depression without the side effects of conventional antidepressants.


Now, a new study is bringing these research topics together, as a team of psychologists sets out to examine the effects of naturally occurring and drug-induced mystical experiences on mental health.

Roland Griffiths, Ph.D., a professor of psychiatry and behavioral sciences at the Johns Hopkins University School of Medicine in Baltimore, MD, led the team to look at the effects of spontaneous and chemically induced religious experiences among thousands of participants.

Prof. Griffiths and colleagues published their findings in the journal PLOS One.

Also, earlier studies generally focused on just one mental condition: depression. This might not provide the full picture.

Previous work has also not quantified how other factors influence this relationship; for instance, people who live alone are more likely to be overweight, smoke, use drugs, and lack social support. So which of these, if any, is the main driver of CMDs?

The authors of the new study aimed to fill in some of these gaps. They looked for links between living alone and CMDs in general, and they investigated which factors seemed to be influencing the relationship.

To investigate, scientists from the University of Versailles Saint-Quentin-en-Yvelines in France analyzed data from 20,503 adults, ages 16–74, living in England. The data came from three National Psychiatric Morbidity Surveys that experts conducted in 1993, 2000, and 2007.


Participants completed Clinical Interview Schedule-Revised questionnaires, which assessed whether they had experienced neurotic symptoms during the previous week.

The surveys also collated data on a range of variables, including height and weight, level of education, employment status, alcohol and drug use, social support, and feelings of loneliness.

As expected, the authors found that the number of people living alone has steadily grown. In 1993, 8.8 per cent lived alone. This is compared with 9.8 per cent in 2000 and 10.7 per cent in 2007.

Their analysis also showed that across all age groups and sexes, there was a significant association between living alone and having a CMD. The size of this relationship was fairly similar across the three surveys.

CMDs were more common in those living alone than those not living alone.

When the scientists delved deeper into the relationship between CMDs and living alone, they found that loneliness explained 84 per cent of the association.

Earlier studies had shown that loneliness is linked with depression and anxiety. Others still had investigated whether loneliness might increase mortality risk.

During what some experts call a “loneliness epidemic,” this finding is particularly important. Similarly, because ill mental health is a growing concern, understanding the risk factors associated with CMDs might help turn the tide.


Of course, not everyone who lives alone is lonely. However, for those who are, interventions to tackle loneliness are available. These may include talking therapies, social care provisions, and animal-based interventions.

The next and most challenging step is to find ways to ensure that people in need get access to these tools.

The researchers acknowledge certain limitations to the study. For instance, this was a cross-sectional study, meaning that it looked at a snapshot of people at one point in time. The authors call for longitudinal studies to ascertain how this relationship might play out over time.

As with any study of this nature, assessing cause and effect is not possible: Did a person develop a CMD because they lived alone, or did they develop a CMD and then decide to live alone?

Or, perhaps, someone with a predisposition for CMDs is more likely to want to live alone. As ever, scientists will need to carry out more work to fill in the gaps.

Earlier findings back up these results, but the new findings also go a few steps further; they show that the relationship between mental health and living alone is stable across time, that the link is not restricted to older adults, and that loneliness plays a pivotal role.

Meanwhile, studies conducted in both animals and humans have found that adverse experiences early in life can have lasting effects on epigenetics, the process by which chemical tags added to a Deoxy ribonucleic Acid (DNA)/genetic material sequence control whether or not a gene is expressed. These studies reported differences in DNA methylation, which can either silence or enhance gene expression, between individuals who were and were not exposed to early-life stressors.


The current study was designed to test the hypothesis that there are sensitive periods during which adversity is associated with even greater changes in DNA methylation.

The investigators also compared that model to an accumulation hypothesis, in which the effects of adversity increase with the number of events, and a recent hypothesis, that the effects of adversity are stronger when events happened more recently.

They gathered data from participants in the Avon Longitudinal Study of Parents and Children, a U.K.-based study that has been following a group of families since the early 1990s.

Participating parents report regularly on many aspects of the health and life experiences of their children, who were enrolled in the study before they were born.

The current investigation analyzed data from a subgroup of more than 1,000 randomly selected mother/child pairs from which DNA methylation profiles had been run for the children at birth and at age seven.

The children’s exposure to adversity before the age of seven was based on whether parents reported their child’s repeated experience of seven stressors: abuse by a parent or other caregiver, abuse by anyone, a mother’s mental illness, living in a single-adult household, family instability, family financial stress, and neighborhood disadvantage or poverty.

The investigators recorded the number of exposures to each adversity, whether or not they were experienced at specific developmental stages and how close they occurred to the age at which blood samples were taken for the second methylation profile.


The analysis identified 38 DNA methylation sites at which adverse experiences were associated with changes in methylation, most of which were associated with when the stressful experience had taken place.

Adversity before the age of three had a significantly greater impact on methylation than did adversity at ages three to five or five to seven.

Exposure to adversity was typically associated with increased methylation, which would reduce the expression of specific genes; and neighborhood disadvantage appeared to have the greatest impact, followed by family financial stress, sexual or physical abuse, and single-adult households.

Although early-childhood experiences had the greatest effects, adversity at older ages was not without an impact. And while the results provide the strongest evidence for the sensitive or “vulnerable” period model, they do not totally rule out any effect related to the accumulation or recency hypotheses. In fact, two of the sites at which methylation appeared to be changed by adversity were associated with either the number of adverse experiences or how recent they had been.

“These additive effects may work together with the timing of exposure, so it would be interesting to examine more complex mechanisms in future studies with larger groups of participants,” says Dunn, an assistant professor of Psychology in the Harvard Medical School Department of Psychiatry.

“Our results need to be replicated by other investigators, and we also need to determine whether these changes in DNA methylation patterns are associated with subsequent mental health problems. Only then will we be able to really understand the links between childhood adversity, DNA methylation and the risk of mental health problems; and that understanding could guide us to better ways of preventing those problems from developing.”


Meanwhile, studying religious and mystical experience, researchers asked 4,285 study participants to answer a survey in which they had to describe their “God encounter experiences and mystical experiences.”

The surveys asked the participants about their experiences with the “God of [their] understanding,” a “Higher Power, Ultimate Reality, or an Aspect or Emissary of God (example, an angel).” The survey also inquired about how the participants felt after the experience and how it changed their lives, if at all.

Approximately 69 per cent of the participants were male, aged 38 years on average, and the vast majority of the respondents were white. The study looked at mystical experiences that occurred both naturally and as a result of taking psychedelics, using two different surveys.

A total of 3,476 participants answered the psychedelics survey, and 809 answered the non-drug survey.

Specifically, in the former group, 1,184 participants took “magic mushrooms,” 1,251 took lysergic acid (LSD), 435 took ayahuasca, and 606 reported taking N,N-dimethyltryptamine (DMT).

“Most participants reported vivid memories of the encounter experience, which frequently involved communication with something having the attributes of being conscious, benevolent, intelligent, sacred, eternal, and all-knowing,” report the researchers.

Overall, the study found that most participants who had “God encounter experiences” reported positive effects on their mental health.


Namely, the mystical experiences improved their life satisfaction, purpose, and meaning, and these positive changes lasted for decades after the experience.

In fact, about 75 per cent of all respondents (in both the drugs and no-drugs groups) said the experience was “among the most personally meaningful and spiritually significant lifetime experiences, with moderate to strong persisting positive changes” to their mental health.

Furthermore, 70 per cent of participants in the drugs group said they had a decreased fear of death as a result of the experiences, whereas 57 per cent of the non-drug participants reported the same feeling.

Approximately 15 per cent of the participants in both groups said the experience was “the single most psychologically challenging experience of their lifetime.”

In the non-drug group, 59 per cent of the respondents described their experience as meeting “God” or “an emissary of God,” whereas 55 per cent of the psychedelics users chose to describe it as an “ultimate reality.”

The lead researcher comments on the findings, saying, “Experiences that people describe as encounters with God or a representative of God have been reported for thousands of years, and they likely form the basis of many of the world’s religions.

“[A]lthough modern Western medicine doesn’t typically consider ‘spiritual’ or ‘religious’ experiences as one of the tools in the arsenal against sickness, our findings suggest that these encounters often lead to improvements in mental health.”

The researcher stresses the fact that their research says nothing about the existence of a higher being. “We want to be clear that our study looks at personal experiences and says nothing about the existence or nonexistence of God.”

Furthermore, the scientists caution that people should not use psychedelic drugs without professional guidance, as there are various psychological dangers to misusing these substances, in addition to legal risks.

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