This year, sugar has replaced fat as the main scapegoat behind obesity and related physical illnesses. However, according to a study by the British Journal of Psychiatry, refined sugar is also linked to the emergence of mental illnesses like schizophrenia and depression (9). Scientists found that refined sugar suppresses the hormone BDNF (brain-derived neurotrophic factor), which is necessary for learning and memory and is found to be low in patients with schizophrenia. Refined sugar also leads to chronic inflammation, which is linked to the emergence of schizophrenia, as well.

While there have been countless studies outlining the correlation between obesity and schizophrenia, most state that schizophrenia causes weight gain due to stress and the side-effects of medications. However, another study in the British Journal of Psychiatry pointed out that while antipsychotic medication does cause weight gain, metabolic syndrome (a set of risk factors associated with obesity) affects 15% of schizophrenics before medication, as well as up to 30% of relatives with similar genetics, but without the disorder (10). Furthermore, there have been 4 large studies in the past several years that show a connection between motherhood obesity and offspring’s development of psychosis; results showed that children of obese mothers were significantly more likely to report hallucinations and schizophrenic tendencies by 21 years old (12).

Perhaps most interestingly, it’s been proven that diet can rapidly change the human gut microbiome, which is a Negative Effects of Sugar (11) collection of microorganisms that live inside the body and heavily influence digestion and immunity (13). In 2015, scientists analyzed the microbiome of patients with schizophrenia and found that it was drastically different than those without the disorder. Specifically, they found that those with schizophrenia had much higher levels of lactic acid bacteria, which are closely associated with chronic inflammation and thrive in environments with high levels of sugar (14).

Cannabis

Cannabis—more commonly called marijuana, weed, or pot—has a steadily-rising 18.1 million users, and is therefore the most frequently used illicit drug in America. According to a study by the University of Michigan, cannabis use among college students is at its highest point in almost three decades, given that 1 in 20 students smokes marijuana daily; in the early 1990s, that statistic was 1 in 50 (15). Combined with the facts that THC content is becoming more potent, synthetic versions are flooding the market, and children are starting to use it at a much younger age (often as young as 12), the link between cannabis and schizophrenia is definitely worth examining (16).

Scientists have found that THC (the psychoactive ingredient in marijuana) causes similar reactions in the brain as schizophrenia. Symptoms like paranoia, disassociation with reality, visual hallucinations, and difficulties distinguishing the passage of time regularly occur, which leads scientists to believe the two instances affect the brain similarly. Both cause parallel hormone releases, like dopamine and glutamine, as well as changes in brain chemistry. As a result, some studies conclude that cannabis may very well prompt psychotic disorders like schizophrenia, especially if someone is genetically predisposed, or starts using at a particularly young age (16).

However, other studies show that cannabis use is significantly higher in the schizophrenic community because patients are simply more likely to use it in the first place. One study in particular (Ferdinand et al.) found that children with prodromal psychotic episodes were more likely to smoke marijuana later on in their lives (17).