Depression in farmers - how pesticides are another mental health stress.

Like any complex chronic disease, depression in farmers and farming families is, well complex. It usually has its origins in stress. This can include economic, family, traumatic stress. But there is a type of stress less well known, but clearly documented within the scientific literature.

It’s agrichemical, pesticide stress, which is clearly documented to contribute to higher than average levels of depression. It's arguably disingenuous to look a farmer in the eye and say - just be resilient, but keep using that mix of sprays on your cereal or horticultural crop.

Chemicals don't work like that.

What do we know?

A landmark 20 year National Institute of Health (NIH) which surveyed 84,000 farmers demonstrated the connection between depression in farmers and use of pesticides.

A 2008 paper ‘Depression and Pesticide Exposures among Private Pesticide Applicators Enrolled in the Agricultural Health Study’ considered the data in the NIH study and confirmed that:

‘after adjusting for state, age, education, marital status, doctor visits, alcohol use, smoking, solvent exposure, not currently having crops or animals, and ever working a job off the farm, pesticide poisoning was more strongly associated with depression than intermediate or high cumulative exposure or a high pesticide exposure event.’

However – there need not be an acute poisoning event to have a higher level of depression:

‘In analysis of a subgroup without a history of acute poisoning, high cumulative exposure was significantly associated with depression.’

The Scientific American & Environmental Health News reported another study using NIH data, writing in 2014:

‘experts say that some of the chemicals used to control pests may make matters worse by changing farmers’ brain chemistry.

Recent research has linked long-term use of pesticides to higher rates of depression and suicide. Evidence also suggests that pesticide poisoning – a heavy dose in a short amount of time – doubles the risk of depression.’

The article discussed the results of September 2014 study using the same NIH data: ‘Pesticide Exposure and Depression among Male Private Pesticide Applicators in the Agricultural Health Study’. The paper advised that:

 ‘two pesticide classes, fumigants and organochlorine insecticides, and seven individual pesticides—the fumigants aluminum phosphide and ethylene dibromide; the phenoxy herbicide (2,4,5-trichlorophenoxy)acetic acid (2,4,5-T); the organochlorine insecticide dieldrin; and the organophosphate insecticides diazinon, malathion, and parathion—were all positively associated with depression’

In this study, use of organochlorine insecticides and fumigants increased the farmer’s risk of depression by 90% and 80%.

The Modern Farmer, which also covered the findings questioned whether ‘farmers were likely to simply have higher levels of depression than the norm, given the difficulties of the job — long hours, low wages, a lack of power due to government interference’ and questioned whether depression may have been over-reported.  The 2014 study lead author Dr. Freya Kamel did not consider so, stating that:

‘In fact, only 8% of farmers surveyed sought treatment for depression, lower than the norm, which is somewhere around 10% in this country. That doesn’t mean farmers are less likely to suffer from depression, only that they’re less likely to seek treatment for it, and that makes the findings, if anything, even stronger.’

An earlier study ‘A cohort study of pesticide poisoning and depression in Colorado farm residents’ which researched the long-term influence of pesticide poisoning on depressive symptoms advised that:

'Pesticide poisoning was significantly associated with depression in three years of follow-up after adjusting for age, gender, and marital status. Depression remained elevated after adjusting for health, decreased income, and increased debt and was primarily due to significant associations with the symptoms being bothered by things and feeling everything was an effort.'

The paper concluded:

'Feeling bothered and that everything was an effort were persistently associated with a history of pesticide poisoning, supportive of the hypothesis that prolonged irritability may result from pesticide poisoning.'

A UK study ‘Neuropsychological and psychiatric functioning in sheep farmers exposed to low levels of organophosphate pesticides’ wanted to understand whether low level exposure to organophosphate pesticides (OPs) causes neuropsychological or psychiatric impairment. The study compared 127 agricultural workers with a history of low level exposure to organophosphate pesticides with 78 non-exposed controls. The study authors noted:

‘A range of emotional, physical and cognitive problems were identified in agricultural workers. In terms of emotional and physical health, over 40% of the exposed cohort complained of clinically significant levels of anxiety and depression compared to less than 23% of controls, the highest rates of distress being found in retired farmers. Farmers also report a range of physical symptoms which they describe as being moderate to severe, the most prominent being fatigue, memory problems, joint stiffness, sleep disturbance, irritability and feeling mentally slowed down.

In terms of cognitive function, general intellectual ability, reasoning, visuo-spatial and verbal ability were relatively well preserved, but agricultural workers obtained lower scores on tests of response speed, working, verbal and visual memory, mental flexibility and fine motor control, than controls.’

A 2013 study 'Pesticide exposure and depression among agricultural workers in France' concluded that herbicides were nearly twice as likely to have been treated for depression than those who didn’t use herbicides, and that this increased if farmers had been using herbicides for more than 19 years.

The scientific literature demonstrates the cost of constant agrichemical exposure to our farming families. Families experience in their own very separate ways, the stress and trauma and misery that accompanies depression and suicide.

Any policy framework, any strategic direction to combat agrichemical stress in farming has an obligation to clearly acknowledge and outline the risks to farmer mental health – but also consider the implications of exposure to neurotoxic pesticides to the family. Particularly women of childbearing age and infants and children. This includes teenagers who have been demonstrated to have vulnerable windows of exposure to developmental toxicants during this time.

This is not happening - risk assessment for pesticides does not pay special attention to full formulation epidemiological studies. Nor does it seek to understand the mechanisms for depression, nor the mechanisms for childhood developmental neurotoxicity. 

The Scientific American article concluded with this comment from a farmer:

“Even if they hear my message, they have to make choices: Do I need to use this chemical for the good of my farm, or do the negative factors – what it could be doing to the insects, food supply and possibly people – make it not worth it?”

Should farmers pay this cost? Or can farmers realistically transition to organic and biological farming with old fashioned state support - bringing back public extension services and government support to facilitate a move in agriculture to agro-ecological farming that will also benefit climate (more carbon in the soil) and environment (less diffuse chemicals in the environment).

It's not just our drinking water, our soil health, our climate that suffers from industrial chemical agriculture.

References:

Beseler CL, Stallones L, Hoppin JA, Alavanja MC, Blair A, Keefe T, et al. 2008. Depression and pesticide exposures among private pesticide applicators enrolled in the Agricultural Health Study. Environ Health Perspect 116:1713–1719; doi: 10.1289/ehp.11091.

Freya Kamel et al, “Pesticide Exposure and Depression among Male Private Pesticide Applicators in the Agricultural Health Study.”  Environmental Health Perspectives, DOI:10.1289/ehp.1307450

Beseler CL, Stallones L. 2008. A cohort study of pesticide poisoning and depression in Colorado farm residents. Ann Epidemiol 18:768–774.

Mackenzie Ross SJ, Brewin CR, Curran HV, Furlong CE, Abraham-Smith KM, Harrison V. 2010. Neuropsychological and psychiatric functioning in sheep farmers exposed to low levels of organophosphate pesticides. Neurotoxicol Teratol 32:452–459.

Marc G. Weisskopf et al, “Pesticide Exposure and Depression Among Agricultural Workers in France.” American Journal of Epidemiology, doi: 10.1093/aje/kwt089