 It is important to note that this study reveals that COAT patients have no domain-specific deficits, which supports the notion that chronic opioid use has minor effects on psychomotor, cognitive, or neuropsychological functioning.Morphine is a highly addictive substance.In controlled studies comparing the physiological and subjective effects of heroin and morphine in individuals formerly addicted to opiates, subjects showed no preference for one drug over the other.