By Dr. Robert K. McNamara, Professor of Psychiatry and Neuroscience, Department of Psychiatry and Behavioral Neuroscience, University of Cincinnati College of Medicine
Serious mental health conditions include the mood disorders, major depressive disorder (MDD) and bipolar disorder, anxiety disorders, psychotic disorders including schizophrenia, and attention deficit hyperactivity disorder (ADHD). In the United States (U.S.), MDD has a lifetime prevalence rate of 16.6%, bipolar disorders 2.5%, anxiety disorders 31.6%, psychotic disorders 1%, and ADHD 10.2%.1,2 There are large variations across countries in the prevalence rates of mental health disorders, particularly for MDD, bipolar disorders, and ADHD, with higher rates observed in developed countries including the U.S. Importantly, the initial onset of mental health disorders frequently occurs during adolescence, and ADHD is typically diagnosed in children prior to 7 years of age. There is also evidence that the age of onset of bipolar disorder is decreasing and the prevalence of ADHD is increasing.2 Among youth residing in the U.S., MDD has a lifetime prevalence rate of 10%, bipolar disorders 3%, anxiety disorders 32%, and ADHD 10.2%.1,2 Therefore, the childhood and adolescent period is associated with high rates of mental health disorders which may reflect increased vulnerability during this critical maturational period. It is notable that mental health disorders in youth increase the risk of suicide, the third leading cause of death in adolescents in the U.S. Therefore, mental health disorders in youth represent a critical and urgent public health problem.
Mental health disorders are commonly initially treated with cognitive behavioural therapy and/or pharmacological medications including antidepressants, mood-stabilizers, and/or second-generation antipsychotics (SGA). However, mental health symptoms commonly return following medication discontinuation, and patients typically require long-term treatment. Long-term treatment with some medications may cause adverse cardiometabolic side-effects, as well as other significant adverse effects, that lead to discontinuation and relapse. For example, SGA medications are generally associated with significant weight gain in youth. Moreover, the first line pharmacological treatment for depression and anxiety disorders in youth are selective serotonin reuptake inhibitor (SSRI) medications, though only 30-40 percent of adolescent patients fully respond to this treatment. These and other limitations associated with these medications highlight an urgent need to develop safer and better tolerated interventions for youth with mental health disorders.
The notion of ‘prevention’ is relatively new to the mental health field. Despite growing interest in early detection methods, there are currently no established treatments. Such ‘prodromal’ interventions will first require a clearer understanding of modifiable risk factors associated with mental health disorders, and need to be safe and well tolerated with long-term treatment. Emerging evidence suggests that dietary modifications may represent one feasible method of reducing the associated risk factors, though additional research is needed to evaluate and refine this approach.
Mental health disorders are thought to be caused by both genetic and environmental factors. Accordingly, some risk factors can be avoided (e.g., drug abuse) whereas others cannot (e.g., a family history of psychiatric disorders). Emerging evidence suggests that diet can have a significant impact on the risk of developing mental health disorders. For example, a Mediterranean diet3 and/or a diet containing fish,4 has been found to be protective against the development of MDD. This is also supported by evidence that different mental health disorders, including MDD,5 bipolar I disorder,6 schizophrenia,7 and ADHD,8 are all associated with low blood levels of long-chain omega-3 fatty acids, which are naturally high in fish. In contrast, the typical western diet, which is high in saturated fats, omega-6 fatty acids, processed sugar, etc, may increase vulnerability. There is also emerging evidence for an association between mental health disorders and deficiencies in Vitamins D and B, zinc, iron, magnesium, and manganese. Animal feeding studies have provided a clearer understanding of how nutrient deficiencies can negatively impact brain development, and neuroimaging studies are beginning to identify the role of specific nutrients in human brain structure and function. Existing evidence therefore suggests that having a diet that includes essential minerals, vitamins, and specific fatty acids, such as omega 3s, is necessary to promote optimal brain development.
Once a mental health disorder develops the underlying pathological brain changes become more difficult to correct. This suggests that nutritional interventions initiated prior to the onset of symptoms may have the greatest therapeutic benefit. Nevertheless, meta-analyses of several different placebo-controlled trials suggest that individuals with established mental health disorders, such as ADHD, MDD, anxiety disorders and early phase psychosis, also benefit from optimizing the nutritional quality of their daily diet – for example, increasing intake of omega-3 with supplementation9,10,11
While it is not currently known how omega-3s reduce symptoms of depression and anxiety, several plausible mechanisms have received experimental support. These include reducing brain inflammation, reducing hormonal responses to stress, increasing nerve growth factors and synaptic connectivity, and promoting circulation in the brain.9 There is also evidence that omega-3s reduce neurodegenerative processes and increase resilience to neurotoxins. It is notable that animal studies have shown that omega-3 fatty acid deficiency during development produces long-standing impairments in different neurotransmitter systems, including serotonin and dopamine, which are thought to play a central role in depression and anxiety. These and other findings suggest that long-chain omega-3 fatty acids may play a role in reducing the risk factors associated with depression and anxiety by several different and complimentary mechanisms.
Unfortunately, diet and nutrition remain largely neglected aspects of mental health practice. This is not unique to mental health and many other fields of medicine, including those more closely associated with diet-related illnesses like cardiovascular disease, rarely consult with their patients about diet and nutrition.12 This has been attributed, in part, to the very limited nutritional education provided to physicians as well as a lack of time and reimbursement for nutrition counselling. Nevertheless, sufficient evidence has accumulated over the past three decades that supports a more central role of nutrition in the management of mental health disorders.13 Although no nutritional intervention is currently approved by the FDA for the treatment of any mental health disorder, the American Psychiatric Association has issued a consensus statement for treating MDD patients with 1 g/d an EPA+DHA.14 This milestone, in conjunction with the availability of FDA-approved omega-3 fatty acid formulations for other conditions, may provide an early foundation to support, diagnosing and treating nutrient deficiencies in patients with mental health disorders.
There is now abundant neuroimaging evidence that mood, anxiety, and psychotic disorders are associated with abnormalities in brain structure and function. These abnormalities include reductions in gray matter, particularly in regions mediating emotion and cognitive processes, as well as widespread reductions in myelin integrity. These abnormalities are accompanied by alterations in the connectivity between brain regions resulting in dysregulated activation patterns. For example, mood and anxiety disorders are associated with greater amygdala activation in response to emotional images, and mood and psychotic disorders as well as ADHD are associated with reductions in prefrontal cortex activation. It is relevant, therefore, that the initial onset of these mental health disorders frequently occurs during adolescence and young adulthood, a period associated with progressive maturational brain changes in the connections between the prefrontal cortex and the amygdala. While it is not currently clear whether mental health disorders are due to abnormalities in brain maturation and/or neurodegeneration, nutrients including omega-3s have been shown to both promote brain maturation as well as reduce neurodegeneration and appear to be a key component in maintaining mental health.
Omega-3 fatty acids have been associated with a wide range of health benefits, discover more.
 R.C. Kessler et al., ‘Twelve-month and lifetime prevalence and lifetime morbid risk of anxiety and mood disorders in the United States.’ Int J Methods Psychiatr Res. 2012;21:169-184.
 G. Xu et al., ‘Twenty-year trends in diagnosed attention-deficit/hyperactivity disorder among US children and adolescents, 1997-2016.’ JAMA Network Open. 2018;1:e181471.
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 J.P. Chang et al., ‘Omega-3 polyunsaturated fatty acids in youths with attention deficit hyperactivity disorder: a systematic review and meta-analysis of clinical trials and biological studies.’ Neuropsychopharmacology. 2018;43:534-545.
 G. Grosso et al., ‘Role of omega-3 fatty acids in the treatment of depressive disorders: a comprehensive meta-analysis of randomized clinical trials.’ PLoS One. 2014;9(5):e96905.
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 A.T. Chen et al., ‘A meta-analysis of placebo-controlled trials of omega-3 fatty acid augmentation in schizophrenia: Possible stage-specific effects.’ Ann Clin Psychiatry. 2015;27:289-296.
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