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Pesticides And Our Mental Health: The Unexpected Link


What do you think of when you think about food? How does it taste, and what does it smell like? Does it look appealing, and will it satisfy my cravings?


Have you ever thought about what else your mid-morning snack might contain? If I told you it contained traces of weedkiller that might increase your risks of depression, would you still eat it?

I’m a junior doctor who recently visited the Stress, Psychiatry and Immunology (SPI) lab at King’s College London. I decided to write this article to raise awareness of a rarely publicised issue which I believe concerns all of us.


It concerns our food and diet, which we now understand plays a vital role in our health and quality of life, far beyond being just ‘fat’ or ‘thin’. It even influences our mental health. It is about the hidden chemicals we might be unintentionally consuming with our wholesome salad, or serving of healthy roasted nuts.


Pesticides, anyone?


How are pesticides linked with our mental health?

Pesticides are substances which control pests and are used in many stages of modern-day food production. They can increase food productivity, prevent crop loss, and help to meet our ever-growing demand for food across the world. For instance, glyphosate is a weedkiller commonly used in the UK, and has been detected in over 60% of wholemeal bread in the UK. However, pesticides are a double-edged sword. Whilst they offer benefits such as making food affordable and readily available, they can also be incredibly dangerous, and few realise the true extent to which we are exposed to these toxic chemicals.



The very nature of a pesticide is to be harmful. Insecticides (which target insects) work by attacking their nervous system, which includes the brain, and controls how the insect moves and responds to the environment. However, insecticides are also toxic to us. Numerous studies over the last two decades have demonstrated links between pesticide exposure and conditions affecting the brain and mental health, such as Parkinson’s Disease, Attention Deficit Hyperactivity Disorder (ADHD), depression, and dementia.


Research from California investigating cases of Parkinson’s Disease, an age-related disease that affects movement and coordination, found that individuals were more likely to be living in areas where certain pesticides had been used. Research on ADHD, found that the odds of having ADHD almost doubled amongst children who were found to have above-average levels of a pesticide-related substance, compared to those without detectable levels of it.




Although it is still unclear how these diseases develop following exposure to pesticides, animal studies suggest that they might cause inflammation of our brains, or affect our neurotransmitter levels, neurotransmitters being the chemical messengers in our brains. For example, certain pesticides have been found to affect levels of acetylcholine, an important messenger which is involved in learning and memory.


Inflammation is a new frontier in mental health research. It has now been connected to just about all mental health conditions. Inflammation itself, is a natural process by our bodies in response to changes and stresses in the environment. But when there is either too much or too little of it, disease may occur, and pesticides have been shown to affect this process.


Should we really be worried?

There is ongoing debate over how concerned we should be about pesticide exposure from food. Some argue that they pose little risk, as we the consumers are at the end of the food production chain and do not directly handle these chemicals.


Others say that there we are only exposed to very small amounts of pesticides, far within ‘safe limits’. This, however, doesn’t address chronic exposure.


We have an average life expectancy of 80 years here in the UK, and we eat food every day. If we consume a small amount of pesticide-tainted food each day for a number of decades, would the risk still be negligible?


Unfortunately, it is difficult to give definitive answers here. Long-term effects are notoriously difficult to investigate, as these studies are known to be expensive, and it is hard to run a study over a period of years which can conclude for sure that pesticides are responsible, as opposed to an individual’s gender, ethnicity, economic or medical background. Generally, available studies seem to determine that pesticides are detrimental to our health.


It is also argued that pesticides are naturally removed from our bodies with other waste products by our kidneys. However, research has demonstrated that they can accumulate in our fat tissue, which means pesticides might stay in our bodies far longer than we once thought. In fact, pesticides have also been found to cross the placenta, an organ which develops during pregnancy that provides nutrients to the fetus. This is particularly concerning, considering there is mounting evidence that environmental factors during fetal development can cause greater vulnerability to anxiety and mood disorders, a concept called fetal programming.


So what now?

With growing evidence that pesticides may be causing mental ill-health, no doubt reducing harmful pesticide use may help prevent it.

Of course, we may be able to reduce our exposure to pesticides by eating foods which haven’t been grown with them. Generally, these products are less mass-produced or grown organically, which prohibits the use of many chemicals which are commonly used in farming such as the glyphosates mentioned before.



True, without pesticides, we may not have enough food at all, and not all of us are privileged enough to afford organic food. Between starvation and the consumption of pesticide-laden food, most people would certainly choose the latter. However, at least with greater awareness of the potential health dangers posed by these chemicals, we may work towards using more and more alternative pest-control measures which could similarly increase yields but without the same potential neurological effects. Contrary to common belief, this is certainly not impossible, as Lechenet and colleagues demonstrated that food productivity does not have to come at the cost of human health.

Certainly, in our society where we are considered more economically developed, we should endeavour towards a community with greater food and health safety.

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