In 1798 the English economist, Thomas Malthus, published An Essay on the Principle of Population. In it he wrote: “The power of population is indefinitely greater than the power in the earth to produce subsistence for man.” Malthus argued that population growth, if left unchecked, would result in mass famine, pestilence and poverty. However, Malthus’s pessimism failed to factor in humanity’s ingenuity and innovation. Technological improvements in food production have, at least for now, averted global Malthusian meltdown. This too, in the face of massive population growth. That said, Malthus’s formula of “more people more problems” seems to hold true for mental health.
One of the largest studies to explore the relationship between population and mental health problems was undertaken in Sweden. This study, published in the British Journal of Psychiatry in 2004, looked at population trends over a four-year period among the entire Swedish population. The study found that greater population density (the number of people per square kilometre) was associated with higher rates of mental health problems, specifically depression and psychosis. Furthermore, as the population density of certain localities increased, typically due to people taking up new employment opportunities, the percentage of people experiencing mental health problems also increased. More people, more problems, let’s call this the Malthus effect.
We recently explored a similar idea using Twitter data for the United States. We found a clear relationship between a state’s population density and the relative negativity or positivity expressed in the tweets of the state’s population. Happier states tended to be those with lower population densities and vice versa. More people, less positivity.
UAE-based research also supports the idea of a Malthus effect. A study published in the International Journal of Geriatric Psychiatry in 2004 explored the levels of depressive symptoms among 610 elderly Emiratis in Dubai, Ras Al Khaimah and Al Ain. The rate of depression for the elderly residents of Dubai was more than twice as high as that reported among the RAK and Al Ain seniors. These findings are open to several interpretations, one being the Malthus effect. Dubai has the highest population density of the three locations in the study.
Another UAE study looked at two different communities in RAK. This study compared rates of depressive symptoms between residents of a relatively sparsely populated community and also among residents of the more densely populated urban community. Both populations were matched for age, gender and nationality. However, the rural residents had markedly lower levels of depressive symptoms.
The most spectacular support for the Malthus effect, however, comes from the work of the celebrated American ethologist John B Calhoun.
Starting his explorations in the 1950s, Calhoun spent two decades looking at the effects of overcrowding in rats and mice. Overpopulation among the rodents in these studies ultimately had catastrophic effects. Overcrowding was associated with increases in aggressive behaviour and the neglect and wounding of offspring (offspring mortality reached 96 per cent in one study).
Eventually, overcrowding would lead to social breakdown, a cessation of reproduction and ultimately the extinction of the population. More rodents, more problems.
We can’t generalise from rats to humans: for one thing we are far more innovative. Just as our innovations helped us fight famine, perhaps an increased investment in psychotherapeutic and psycho-educational technology will help us counteract the psychological aspects of the Malthus effect. Since the middle of the 20th century, the Arabian Gulf’s population increased seven-fold. If we are to continue to flourish, we certainly need to explore new ways of ensuring that we can feed our psychological needs.
Dr Justin Thomas is an associate professor at Zayed University
On Twitter: @DrJustinThomas