Search Results
The search identified 2931 papers fitting the eligibility criteria, with 2681 remaining after de-duplication. The abstracts and titles of those records were then screened and 2511 were excluded due to not meeting the inclusion criteria. This resulted in 170 papers for full-paper screening. A further 130 papers were excluded during this stage, for reasons shown in Figure 3. The remaining 40 full-text papers were used in the narrative synthesis. Data from these papers including study design, sample, medication (name, dosage), pre-intervention treatment, placebo (yes/no), social cognitive domains tested, social cognition measures, follow-up timepoints, key findings, and study limitations, were extracted and can be viewed in Table 1. Notably there were no studies of mood stabilisers, barbiturates, pregabalin or any sedative antidepressants.
Quality of Assessment of Studies
Data quality was rated by ZH on all 40 full-text papers and AJW on 20% randomly selected papers. An interrater reliability score Cohens Kappa Coefficient of 0.85 was calculated [41], indicating good agreement between authors. Of the 40 included papers, 11 were rated poor and 20 were rated fair. Only 9 total papers were rated good, and none were rated excellent. Scores for each paper are reported in Table 1.
Benzodiazepine Studies
Four benzodiazepine studies conducted in healthy volunteers showed significant impairments in emotion recognition social cognition tasks following diazepam administration [42-45], suggesting that sedative medication at a therapeutic dose impairs emotion processing. One of these papers also incidentally investigated the effects of Metropolol, a beta-blocker with mild sedative effects, and found no significant effect of the drug on emotion recognition [45]. A further study [46] showed a selective effect of diazepam on recognition of angry expressions only. This result may be due to using a small dose in comparison to other studies. One benzodiazepine study using oxazepam showed no effect on a measure of empathy [47].
One study was conducted in patients with schizophrenia, which looked at the effects of benzodiazepine withdrawal. Patients who were in the process of withdrawing from benzodiazepines were significantly impaired in recognising negative emotions compared to healthy volunteers, in contrast to patients who had already withdrawn, who were not. However, all patients were likely to have been on other medications [42].
Neuroimaging studies of benzodiazepines and social cognition
All neuroimaging studies compared social cognition before and immediately after administration of the experimental drug. Del-Ben et al [48] showed that a single dose of diazepam in healthy volunteers resulted in attenuated activation of the right amygdala when responding to fearful faces, although no evidence was found for this interaction when participants viewed angry faces. In another healthy volunteer study, Paulus et al [49] showed that lorazepam attenuated activation in the amygdala and insula, and that the activation was significantly lower after 1mg compared to 0.25mg, suggesting a dose-dependent reaction in emotional processing regions. However, a study by Olofsson et al [50] found no interaction between benzodiazepines and EEG activity during response to an affective processing task.
A study investigating benzodiazepine effects on patients with ‘catatonic’ schizophrenia and patients with bipolar disorder found that lorazepam induced BOLD signal decreases in the occipital cortex and medial prefrontal cortex (MPFC) in patients with schizophrenia when undertaking a negative emotion recognition task. This resulted in BOLD patterns resembling those of healthy volunteers taking a placebo drug during the same emotion recognition tasks [51]. However, at the time of the fMRI task all patients were taking either antipsychotic or antidepressant medications in addition to the administered lorazepam.
Antipsychotic Studies
Healthy volunteers
Only two studies tested the effects of antipsychotics on social cognition in healthy volunteers. A small crossover study by Lawrence et al [52] (N=14) found that recognition of angry facial expressions was reduced in participants taking sulpiride, but recognition of other expressions was not affected. In addition, a larger randomised parallel group trial of quetiapine versus placebo by Rock et al [53] (N= 27) found no effect of the medication on facial expression recognition, though dropout rates were high (25%) in the quetiapine arm, which may have obscured an effect.
Patient studies
All studies comparing patients with schizophrenia and healthy volunteers found patients performed less well on social cognition tasks whether or not they were taking antipsychotics at baseline [54-63]. This included one study with patients who were drug naïve [55], two studies with patients who were drug-free at study commencement [59, 63], studies including participants with a mixture of drug-naïve, drug-free, and previous treatment for under 4 weeks [56-58, 60, 64, 65], and one study with patients stable on an antipsychotic [66]. Most longitudinal studies involving people with schizophrenia taking antipsychotics showed improvements in performance on social cognition tasks at follow-up compared to baseline [55-58, 61, 62, 67-71], although some found no effect [54, 59, 60, 66, 72-75] and one showed a decline [63].
When studies were classified by the prior medication status of participants, two longitudinal studies involved patients who were previously drug naïve. One of these studies detected improvements on an emotional processing task at follow-up [55], the other study involved an attributional style task, and found no effects of the medication [54]. Studies that involved patients who had a prior drug-free period, mostly found improvements in emotion processing tasks [56, 58, 59, 70], and one in a theory of mind task [61]. Some studies specified that participants were taking an antipsychotic at baseline prior to switching to another [57, 60, 62, 63, 66, 67, 69, 71-75] and one did not describe the prior treatment status of participants [68]. In studies in which people were already taking antipsychotic treatment, results reflect effects of changing the type of antipsychotic rather than starting treatment.
One study tested healthy volunteers at baseline and follow-up to control for practice effects [56]. It found that patients with schizophrenia treated with antipsychotics (a mixture of people who were previously drug naïve (n=11) or drug free (n=12)) showed significant improvements in emotion recognition at 6 months compared to healthy volunteers.
One longitudinal study involving 29 people with schizophrenia and 28 with bipolar disorder explored dose-response relationships [63]. Findings showed that patients with schizophrenia who were taking higher doses of antipsychotic medication had more difficulty recognising sad and neutral facial expressions compared to those taking lower doses at follow-up. In bipolar patients, antipsychotic dose was unrelated to the accuracy of performance in judging emotions.
Studies comparing different antipsychotics produced inconsistent results. Some found that patients treated with second-generation drugs did better than those taking first-generation antipsychotics [67-70, 76], but there was no consistent pattern to the results. Others found no difference between different agents or types of agent [64, 65, 72-75]. The largest study by Penn et al [71] showed improvements in all treatment groups (except for ziprasidone) on an emotion processing task, with no difference between individual second-generation drugs or between first- and second-generation drugs.
One study involving participants with Huntingdon’s disease showed poorer performance on facial recognition tests in those taking antipsychotics compared to those who were not, after controlling for the stage of the disease [77].
In this review, several studies were conducted by authors who received funding from pharmaceutical companies for research purposes or consulting. One study had a pharmaceutical company provide the medication for the research [72]. Studies that were conducted by authors who received pharmaceutical company funding found either improvements in social cognition after antipsychotic administration [67, 71, 78], or no effect of the drug on performance [62, 72, 74]. However, improvements were also shown in studies that did not rely on pharmaceutical funding [55-58, 61, 68].
Neuroimaging studies of patients and social cognition
A study by Sumiyoshi et al [78] investigated the effect of the antipsychotic, perospirone, on social perception in schizophrenia patients. They found an increase in the P300 ERP activation in the left pre-frontal cortex (PFC), as well as improvements in the social cognitive script task, after six months treatment compared to baseline.
A study investigating the effect of sultopride on emotion processing in healthy volunteers found decreased BOLD responses in the amygdala when viewing negatively valenced stimuli compared to before sultopride administration [79]. There was also increased activation in the PFC identified during positron emission tomography (PET) scans. However, behaviourally they found minimal changes to performance on social cognition tasks. Additionally, a crossover EEG study by Franken et al [80] with healthy volunteers, found that both the dopamine agonist bromocriptine, and antipsychotic haloperidol produced no significant difference in emotion-related ERPs (P300-P400) compared to before drug administration. This study used low doses of medication, however, and some participants were also prescribed domperidone to treat nausea.