What if a simple scratch-and-sniff test could predict successful outcomes from psychosocial interventions for people with schizophrenia? That’s the primary question we are asking in a NIMH-funded study linked to Project SUCCESS, which is titled, “What the Nose Knows: Hedonic Capacity, Psychosocial Interventions and Outcomes in Schizophrenia.” Specifically, my colleagues and I aim to determine if hedonic (pleasantness) ratings of different smells predict how much people with schizophrenia benefit from the two evidence-based psychosocial interventions—Cognitive Enhancement Therapy (CET) and a form of Social Skills Training (SST) called Helping Ourselves Perceive and Experience Success (HOPES)—that they receive through their participation in Project SUCCESS. In essence, just scratching, sniffing and identifying nine odors, then rating the odors’ pleasantness, could provide meaningful information about a person’s potential benefits from CET and SST. We are also investigating the relationship between the hedonic smell ratings, the ability to experience pleasure from various activities, and clinical symptoms. Finally, we seek to analyze how medication type—clozapine or other antipsychotic medications—may interact with hedonic smell ratings to influence the effectiveness of CET and SST.
Why examine hedonic capacity or any component of reward as a factor influencing CET and SST outcomes, and why specifically choose olfactory probes? We know that reward processes play a vital role in learning and social interactions, and there has been increased attention to the link between reward circuitry dysfunction and the cognitive, emotional and behavioral challenges of schizophrenia. While there are several measures of reward system processes, accumulating behavioral and neuroimaging evidence suggest that abnormalities in reward system functioning may be probed by olfactory stimuli, and a growing number of studies have used the olfactory system to probe hedonic capacity across the psychosis spectrum. Other appealing aspects of olfactory assessments are that most standardized olfactory measures are simple, fast and inexpensive to administer, reliable across a wide range of ages and conditions, tolerable (and even fun for many), not associated with cognitive deficits, less susceptible to symptom fluctuations than questionnaires and some behavioral indices, and correlate with negative symptoms of schizophrenia.
We hypothesize that those with the largest range of olfactory hedonic ratings between the most pleasant and unpleasant odors (i.e., the greatest olfactory hedonic capacity) will show the greatest improvements on outcome measures in both the CET and SST groups. Secondarily, we expect that those treated with clozapine will show a broader range of olfactory hedonic ratings between the most pleasant and unpleasant odors, and thus better outcomes, than those treated with other antipsychotic medications (based on preliminary data suggesting that clozapine treatment is associated with broadening and strengthening the hedonic experience of olfactory stimuli). And, finally, we anticipate that those with greater olfactory hedonic capacity will display greater improvements on other measures of reward and clinical symptoms, including negative symptoms, motivation, anticipatory and consummatory pleasure, and explicit reinforcement learning. The findings from this study are expected to help predict who may benefit most from these psychosocial treatments, and suggest new therapeutic approaches or the refinement of existing interventions (e.g., the incorporation of targeted reward-enhancing strategies) to improve outcomes for individuals with schizophrenia-spectrum conditions.
Raquelle I. Mesholam-Gately, PhD