Research round-up: depression

Social isolation and lockdowns during the COVID pandemic have contributed to a rise in depression rates.Credit: Matthew Horwood/Getty

Depression rates rose when COVID-19 struck

Rates of depression during the early months of the COVID-19 pandemic were several times higher than the most recent global estimate of the condition’s prevalence, reports a team of researchers in Spain. The meta-analysis confirms what many have long suspected: viral threats, lockdowns and social isolation chip away at mental health.

The team examined 12 studies of depression prevalence from a range of countries, including China, Italy, India, Denmark and the United Kingdom. Most of the studies included at least 1,000 people. The depression rate recorded between January and May 2020 — after the COVID-19 outbreak had begun in each country — ranged from 7% to 48%, with an average of about 25%.

Even the lowest rates seen in the study surpassed pre-pandemic levels, which the Institute for Health Metrics and Evaluation in Seattle, Washington, had pegged at 2–6% globally, and the 25% average was about 7 times higher than a 2017 baseline of 3.44%. These depression rates were also generally higher than those seen in previous epidemics such as SARS and Ebola.

The authors think that their results underscore the need to incorporate mental-health awareness into COVID-19 public-health responses. They note that amid uncertainty, mortal threat and social deprivation, depression is often a natural result — one that can be anticipated and planned for to minimize its impact.

Int. J. Clin. Health Psychol. 21, 100196 (2021)

AI detects depression in online messages

A machine-learning platform developed by scientists in Australia can detect signs of depression in messages people post on social media. Such a platform could potentially alert care providers to posters’ mental-health struggles before more obvious depression symptoms appear.

The researchers trained their artificial-intelligence (AI) system on more than 20,000 Twitter messages from a variety of posters — some of whom had been diagnosed with depression. By reviewing these messages, the AI system learnt subtle factors that set messages from people with depression apart from the rest.

To test the system’s performance, the researchers fed in other texts from social-media sources such as Facebook and Reddit, as well as from the online journals of a 17-year-old girl who had recorded her own experiences with depression. In most trials, the system proved 70–99% accurate at distinguishing between messages from people with depression and those without — even if these messages did not explicitly mention depression.

The researchers think the system might be useful to help identify people who could benefit from mental-health treatment — and down the line, it could be used to monitor population-wide mental-health trends. As with many health-related AI systems, however, social-media companies will have to navigate a thicket of privacy concerns if they plan to use such technology to monitor user activity.

Comput. Biol. Med. 135, 104499 (2021)

Controversial therapy halves suicide risk

Although often maligned as too invasive, electroconvulsive therapy (ECT) is an important bulwark against suicide in people who are severely depressed, according to researchers at the University of Toronto in Canada. When people with severe depression received ECT, their risk of dying by suicide decreased over a 12-month period.

In the study, the researchers analysed health data from people with depression who had been admitted to psychiatric hospitals in the province of Ontario, Canada — a total of more than 67,000 participants, about 5,000 of whom were prescribed ECT following their admission.

Within one year of their hospital discharge, people who received ECT were about half as likely to die by suicide as were those who did not receive ECT — a risk reduction similar to that seen in people on lithium treatment. In addition, those who received ECT in the study were 25% less likely than their untreated counterparts to die of any cause during the same time period. The reduced risk of suicide was greater in people with unipolar depression (often called major depression), than in those with bipolar disorder, perhaps because bipolar illness is associated with longer-term mood symptoms and repeated relapses.

As the researchers acknowledge, ECT can cause significant side effects, including memory loss and problems with cognition. Yet they see their study as proof of ECT’s continued usefulness in people who are severely depressed, arguing that its life-saving effects should not be discounted. The team also points to research that is evaluating magnetic seizure therapy, a gentler treatment that delivers a lower electrical charge to the brain, to see whether it offers equally robust protection against depression and suicidal thoughts.

Lancet Psychiatry 9, 435–446 (2022)

Moderate exercise reduces depression

People don’t have to become regular gym-goers to lower their risk of depression, according to a meta-analysis of exercise studies. Small changes to a person’s routine, such as walking 15 minutes to and from work each day, can substantially transform their mood and outlook.

Researchers looked at 15 studies that tracked people’s moods and physical activity. The data they amassed accounted for millions of hours worth of exercise, including, for example, brisk walks, sprints and triathlons — they found that even a modest exercise routine conferred big mental-health benefits. When people did just over one hour a week of low-intensity exercise (such as brisk walking), they were 18% less likely to be depressed than were those who did not exercise. Bumping up the dose increased the benefit: people who logged 2.5 hours of low-intensity exercise a week were 25% less likely to get depressed.

The researchers point to a range of possible explanations for why exercise might lower the risk of depression, including better post-workout self-image and release of euphoria-inducing ‘runner’s high’ compounds in the brain. The results suggest health-care providers should recommend modest exercise routines — not just to maintain overall health, but to prevent future depressive episodes.

JAMA Psychiatry 79, 550–559 (2022)

How heart health links to depression

Cardiovascular health does more than determine lifespan — it can also shape people’s day-to-day outlook and well-being. A study conducted by researchers in Spain found that older people with certain heart-disease risk factors were more likely to report being depressed than were those with lower cardiac risk.

The study analysed data from the PREDIMED-Plus trial, a 6-year study of more than 6,000 overweight older people (men aged 55–75 and women aged 60–75). Participants were placed into low, medium and high cardiac risk groups on the basis of factors such as their cholesterol levels, blood pressure, diabetes status and smoking habits. The team then followed the group for two years, tracking cardiovascular and mental health.

Data analysis identified several cardiovascular risk factors that were highly predictive of depression. Total cholesterol of 280 or higher was linked to a 31% increased risk of depression, and a diastolic blood-pressure reading of 100 or higher conferred a 50% increased risk. Furthermore, people with diabetes were 39% more likely to be depressed than those without diabetes.

The association between cardiac risk factors and depression was strongest in women — those in the highest cardiac risk group were 78% more likely to develop depression than were those in the low-risk group. Heart-disease risk and depressed mood, the researchers state, might be linked because some of the same physical processes that cause heart disease, such as inflammation, blood vessel deterioration and reduced insulin sensitivity, are also thought to contribute to the onset of depression.

PLoS ONE 17, e0265079 (2022)

Inflammation tied to genetic depression

People who have genes that increase their risk of depression also tend to have higher counts of white blood cells, indicating some level of inflammation in the body. This finding, from researchers in the United States, hints that the immune system might play a key part in the onset of depressive symptoms when genetic risk factors are already present.

To perform their analysis, the scientists tapped into biobanks in the PsycheMERGE network, which stores genome data and laboratory results from hundreds of thousands of people. In a sample of more than 380,000 people from the network, the team identified those who had high-genetic-risk scores for depression, then tested for correlations with more than 300 different clinical laboratory measurements.

Members of the genetic high-risk group turned out to have higher levels of white blood cells overall, as well as high levels of specific immune cells, such as monocytes and neutrophils. Although elevated, the counts generally fell in a normal reference range, meaning physicians would not suspect full-fledged infection in these cases. Researchers had previously known that some immune biomarkers — such as white blood cells and C-reactive proteins — were tied to depressive signs. This study, however, went further by linking immune-cell counts with people’s genetic susceptibility to depression.

The team does not yet know whether depression-related genes drive inflammation, or whether immune activation triggers a genetic tendency to depression, or some combination of the two. Further study of immune markers might help to clear up some of these unknowns — and with a strong research foundation, tests for certain immune cells could one day be used in depression prevention and treatment.

JAMA Psychiatry 78, 1365–1374 (2021)

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Elizabeth Svoboda