Comorbid drug addiction and mental illness appears to be just one of innumerable manifestations of the philosophical conundrum known as the chicken-egg debate. Even if the clinical literature has intimated an inexplicable link between the entwined phenomena, nobody can profess with any quanta of confidence as to whether the implied relationship is causal or correlational; is mental illness the dreaded Stygian precursor of substance addiction or is the latter the humus from which the former springs forth?
It is now a widely accepted fact that roughly 50% of persons suffering from schizophrenia are also addicted to substance abuse, usually alcohol or cannabis. Just as a bitumen road may trifurcate and illumine three unknown destinations for its traveler, so too is the elevated prevalence of substance use disorders in individuals with schizophrenia explicable in the context of three chief theoretical orientations. Some of these theories suppose mental illness to precede substance abuse, others the inverse, and others still that a third discrete variable motivates both. In the neural-diathesis stress model, constitutional genetic and neurobiological vulnerability to psychopathology interacts with environmental stressors like psychoactive substance abuse to generate full-blown clinical symptoms. The accumulative risk-factor hypothesis, on the other hand, argues that subpar cognitive, social, and vocational functioning coupled with continued subsistence in hostile social environments would naturally render individuals much more susceptible to substance abuse. Last but definitely not least, the self-medication hypothesis attempts to explain substance use in individuals with schizophrenia as a deliberate attempt to ameliorate the dreaded extrapyramidal side effects of antipsychotic medications. There are viable alternative explanations too, namely the reward circuity dysfunction, however these will not be discussed here.
Each model enjoys differential support from clinical and experimental studies, indicating that one size does not fit all and that unique coagulating and “esemplastic” powers of the environment molding a particular individual determine which shall be veridical or not. Recently, I found myself cogitating which of these theoretical orientations may have the most explanatory power for a first cousin of my father’s who received a dual diagnosis of schizophrenia and hallucinogenic use disorder when he in his early twenties.
It appears Chris was a cheerful denizen of the imaginal realm from birth, preferring to lose himself in the waves of magical thinking and rebelliousness than to stand upon the shores of rational analysis and orthodoxy. He was the kind of child who frequently heard haunting whispers in the wind. “That dint in mental furniture runs on our side of the family and has been passed down from generation to generation,” my father once told me, or so he believes. During his formative years Chris spent ample time collecting and dissecting insects and drawing anything and everything that impressed him. His eccentricity, nonconformity, and tendencies to novelty and experimentation were only shadowed by a robust curiosity towards the many marvels of Mother Nature.
Chris was moved by the natural world but more so by the preternatural and the sinister, murkier aspects of the human condition. At his best he was an inspired maverick however at his worse he was reckless and slight anarchistic too. His visual art was always visceral, carnal, avant-garde, and colorfully evocative. Under the tutelage of his supportive parents and a cooperative inner muse, his hyperactive imagination spewed forth mythological statuettes, ornaments, paintings, and variant genres. He graffitied onto trains and factory walls and allowed goblins, mythological creatures, and extraterrestrial beings which had erupted from his psychic unconscious to come life through visual sequences and narratives. He was extremely versatile and prolific as a creator, using his tutored hands to create an abundance of artistic works in naturalist, surrealist, and more abstract representational styles.
In his early adult years, perhaps around the age of eighteen, Chris started experimenting with psychostimulants like cocaine and methamphetamines as well as depressants like cannabis. At heart an empathic, compassionate, and benevolent individual he found it almost impossible to refuse requests made by acquaintances to provide a homely and relatively venue for communal drug use. From my father’s assertions Chris was an ill-fated victim of peer pressure. “He couldn’t say ‘no’ to save his life,” my father professes. “On weekends his parents would sojourn at their beautiful holiday house in Rye on the Mornington Peninsula, and that’s when the group festivities involving liberal and copious use of drugs would transpire. He and his friends would gather at the home on Friday and Saturday nights, either drinking or using drugs.”
Unbeknownst to his parents, Chris suffered an acute psychotic break not long after the inauguration of the drug use and it was not long before the benign whispers and driving melodies emanating from the wind and the non-conventional esoteric ideas surrounding creation morphed into poignant multimodal hallucinations and paranoid delusions. Once pregnant with collective meaning, the “strong imagination” that had served as both a powerful ally against dis-ease and a viable source of income degenerated slowly into a self-sabotaging demon of faulty reality testing, an entity cocooning itself inside an artificial world with no yoke or thread to consensus reality. The drug use continued intermittently and as the years went by Chris slipped further and further into the rabbit hole, ensnaring himself a psychical dimension where the news reporter would communicate ideas and instructions to him directly, “The Others” would not allow him to depict certain scenes and images artistically, and the FBI had installed microchips and undetectable surveillance equipment in the house along with minute video cameras in the backyard in an attempt to discover the most intimate, microscopic details of his life and then use them against him. In the last two decades Chris has been beleaguered by psychotic symptoms and chemical dependency, at times appearing like an insurmountable, stoic knight in shining armor and at others like an unassuming zebra caught in the lethal jaws of the dreaded African crocodile.
Blatantly obvious here is the notion that at some point in his life trajectory something interacted adversely with his existing genetic and neurobiological makeup to augment the positive schizotypal qualities intrinsic to his perceptual interface into full-blown clinical expressions of faulty and compromised reality testing. That much is certain. In retrospect, phenomenological hallmarks of creativity and artistic talent like preferences for novelty, attenuated latent inhibition, and hyperassociation which present themselves in differential amounts in both the highly creative individual and the hallucinating psychotic were salient in Chris from very early childhood, if not birth. To explain the early expression of this slightly disorganized perceptual phenotype one learned in the cognitive neurosciences might speculate copious excesses of synaptic pruning which then occasioned functional disconnectivity of fronto-temporal and auditory networks along with structural abnormalities in his medial-dorsolateral prefrontal cortex and anterior cingulate cortex. The formative wiring of Chris’s brain was different to yours or mine. And while we’re not sure when this ‘abnormal’ phenomenon may have occurred during his childhood and early adolescent years or even the number of times it may have occurred, we can be very certain that it did occur.
With lower than normative functional connections between frontal lobe regions responsible for self-related processing and set shifting and the lower-perceptual areas, namely the medial-superior temporal lobe regions, Chris’s maturing brain was already prone to irrelevant sensory processing and diminished sensory gating, task-irrelevant activity, illogical deductions, perseveration, and tendencies to brood on inner experience. For a while this didn’t pose any major problems in day-to-day functioning because the existing executive (prefrontal) level of inhibitory, metacognitive control over lower-perceptual regions (encompassing implicit memory and responsible for the generation of primary process thinking) was sufficient to keep his perceptual interface anchored to the social world and flexible enough as to be able to take advantage of bizarre thoughts and novel ideas without being overwhelmed by them.
The lamentable lapse occurred when a further atypical modification to the neurochemistry led to top-down failure, enabling now completely disinhibited attractor states in the superior and medial temporal lobes to involuntarily interject primary process material into conscious awareness and manifest as subjective experiences of auditory verbal hallucinations. What, you ask, is it that changed the existing biochemistry? And was is natural or synthetic? To all intents and purposes the corroborating evidence–both anecdotal/eyewitness and theoretical–converges on the view that the relatively modest cocktail of psychoactive substances taken orally and injected intravenously during his late teenage and early adult years instigated an acute psychotic episode from which he never truly recovered. Over time the sustained use of methamphetamines probably compromised grey-matter density in the middle and bilateral superior temporal gyri and axonal (white-matter) pathways for the fronto-temporal network, increasing the severity of his hallucinations and delusions and rendering his perceptual mechanisms and behaviors much less amenable to external correction. These days Chris will more frequently cede ground to the demons of psychopathology than not.
To conclude I will profess that this particular dual diagnosis case fits the neural diathesis-stress model like a glove–the egg (substance abuse) mingled with a third variable (phenotypic variant of normative perceptual interface) to produce the chicken (schizophrenia or psychosis)! However, what is veridical here may be outright erroneous for a different case.