Cognitive deficit in psychosis: an illustrious unknown
An interesting work by UCLA (McCleery et al., 2019) collected 47 clinical studies that used MCCB to evaluate cognitive impairment in psychotic disorders considering three groups of subjects: 1) individuals with recent psychotic onset; 2) subjects at high genetic risk for the development of a psychotic disorder, for example detecting the presence of first-degree family members probable for schizophrenia; 3) individuals at high clinical risk for the presence of prodromal signs and symptoms of a psychotic disorder.
Advertising message DSM 5 (APA, 2013) defines the key characteristics of psychotic disorders according to five areas: delusions, hallucinations, disorganized thinking, abnormal motor behavior and negative symptoms. In general, cognitive impairment does not appear among the diagnostic criteria that contribute to the diagnosis. Although various studies agree in defining cognitive impairment as one of the first clinical signs that emerge in psychotic disorders, it is the last one that is diagnosed and often not treated. Consider that the incidence of cognitive deficits is estimated in 80% of psychotic subjects, a percentage that rises to 98% in subjects diagnosed with schizophrenia (Keefe et al., 2005).
The effect of this diagnostic gap can be decisive in the outcomes of the treatment, since the cognitive deficit can be persistent even after an improvement in the general clinical picture and, in fact, be decisive in the patient’s disability. In fact, cognitive impairment in psychotic subjects correlates with various aspects of functioning (daily, work, social) and can contribute to exacerbating symptoms, social isolation, relationship difficulties, with serious repercussions in the quality of life (Tripathi et al., 2018).
In 2004, the National Institute of Mental Health (NIMH) developed the MATRICS (Measurement and Treatment Research to Improve Cognition in Schizophrenia) initiative in order to reach a general consensus of the scientific community about the criteria and methodologies to be used in the evaluation. cognitive of the psychotic subject (Marder et al., 2004). From this work, the MCCB – Matrics Consensus Cognitive Battery (Nuechterlein et al., 2006) has been developed, currently translated into 20 languages. The battery explores 7 domains: attention and vigilance, working memory, speed of execution, verbal learning, visual learning, reasoning and problem solving, social cognition.
An interesting work by UCLA (McCleery et al., 2019) collected 47 clinical studies that used MCCB to evaluate cognitive impairment in three groups of subjects: 1) individuals with recent psychotic onset (-recent onset- RO), within one year of diagnosis; 2) subjects at high genetic risk for the development of a psychotic disorder (-genetic high risk- GHR), detecting for example the presence of family members of first degree proband for schizophrenia; 3) individuals with high clinical risk (-clinical high risk- CHR) for the presence of prodromal signs and symptoms of a psychotic disorder. Regarding the weight and severity of the impairment, the results show a cognitive deficit in each of the domains evaluated in the RO group (from -.74 to -1. 20 ds) with only a slight saving in performance in working memory and in social cognition compared to subjects with chronic forms of schizophrenia. Longitudinal studies on cognitive impairment in the GHR group show an attenuated picture, however consistent with the subsequent development of psychotic symptoms. Within the CHR group, similarly to what was observed in the GHR group, cognitive deficits were observed only within the group of subjects who subsequently developed a psychotic disorder (CHR + group). With regard to the course, the results derived from the longitudinal studies show a stability of the cognitive profiles over time both in the CHR + group and in the RO group. On the other hand, a certain heterogeneity of the results was found during the chronic phase of psychotic disorders. specifically, considering the trend of the cognitive deficit in a longitudinal study with schizophrenic subjects, a stability over time was found in 50% of the subjects, a modest decline in 40% and a marked impairment in the remaining 10% (Thompson et al., 2013) . A worsening of the picture is associated with various factors such as the age of onset of the disorder, the severity of the negative symptoms and residential resources (the most penalized seems to be those who live alone).
Advertising message Regarding treatment: research indicates modest, and in some cases harmful, benefits of antipsychotic drugs on cognitive performance (Woodward et al., 2005; Hori et al., 2006). Furthermore, the results of the studies that determine the differences between typical and atypical antipsychotics are inconsistent in relation to the measurement of cognitive performance. Some research has found a modest improvement in cognitive deficit, especially regarding working memory, through a glutamatergic and cholinergic approach.
Compared to cognitive training (CT), the analyzes substantially show an improvement in cognitive performance, which however does not seem to have a high ecological transfer in the functioning of daily life (Wykes et al., 2011). In other words, TC works if it is repeated in continuous cycles and if it is included in articulated rehabilitation programs.
The increase in cognitive performance through neurostimulation programs (for example transcranial electrical stimulation) is an interesting research area for now, but the literature on it is still rather scarce.
The current state of research suggests that cognitive impairment: 1) is always present in a psychotic disorder and is the cause of disability, 2) in some cases it precedes its onset, 3) affects many cognitive domains, 4) is relatively stable in time if left untreated, 5) requires a multidimensional approach.
Since cognitive performance is linked to the efficiency and functional efficacy of the subject in many aspects of his life, it would be appropriate to include the treatment of cognitive deficit among the main therapeutic objectives in the treatment of psychotic disorders.