In addition to its associated psychosocial risks, active psychosis may affect the brain in a more fundamental way. It has been suggested that psychosis may be neurotoxic and that acute psychotic exacerbations represent active periods of a morbid process that leads to disease progression and to impairment of treatment response [
4,
44,
45]. Supportive evidence was initially provided by the well replicated finding that a longer duration of untreated psychosis is associated with a poorer long-term outcome [
46]. Similarly, relapses also represent episodes of active psychosis and may also be associated with illness progression. However, to date there is limited empirical evidence to support the neurotoxic psychosis hypothesis, and specifically for illness progression after relapse. A search of the literature revealed the following: 1) Treatment response has been observed to be better in first-episode schizophrenia than in chronic multi-episode schizophrenia [
45]. 2) A study utilizing the neuroleptic threshold principle found that first-episode patients required lower doses of haloperidol to achieve optimal clinical response than multi-episode patients [
47], raising the possibility that tolerance to the effects of antipsychotics may develop. 3) Eighty % of patients with schizophrenia were judged to have deteriorated over time in a 7-yr follow-up study, and the degree of deterioration was significantly correlated with the number of relapses that patients experienced [
48]. 4) In another long-term follow-up study of the natural course of schizophrenia, Wiersma et al. examined the course of patients over the first four psychotic episodes. They reported a remarkable observation, namely that, on average 1 in 6 patients failed to remit after each episode, irrespective of which episode it was. 5) More direct evidence was obtained in a preliminary study comparing treatment response times of first and subsequent episodes, where median (SE) times to remission were significantly longer for the second episode and third episode [
4]. On the other hand, there is evidence to suggest that disease progression does not occur as a consequence of relapse: 1) It has been reported that patients’ symptoms rapidly return to baseline with resumption of antipsychotic medication shortly after recurrence of psychotic symptoms [
49]; 2) In patients with relatively refractory schizophrenia who were exposed to placebo treatment for at least 6 weeks and experienced symptom worsening, it was found that, given a sufficiently lengthy recovery period, symptom levels returned to those of baseline [
50]; 3) Response trajectory analyses in early psychosis suggest that, while some patients respond poorly initially, response is generally characterised by amelioration [
51]; 4) The clinical and neurobiological evidence for neurotoxicity of psychosis has been reviewed and found wanting [
52]; 5. Finally, a recent paper challenges the concept of schizophrenia as a progressive brain disease, arguing the following: a) While longitudinal studies report a poor outcome in approximately 25% of patients, few of them describe incremental deterioration that would characterize neurodegenerative disorders; b) while some neuro-imaging studies report brain tissue volumes decreasing over time, this could be attributed to the effects of antipsychotic medication, substance abuse, effects of lifestyle or elevated glucocorticoid levels associated with chronic stress; c) cognitive functioning does not appear to deteriorate over time; and d) the deterioration that occurs in some patients could reflect poor access, or adherence, to treatment, the effects of concomitant conditions, and social and financial impoverishment [
53].
We were able to compare treatment response before and after relapse in both a first-episode [
12] and a multi-episode [
11] sample. We found that in both groups treatment response was highly variable, with some patients rapidly returning to pre-relapse symptom severity levels, and others having a more protracted recovery. Most notably, we found evidence of emergent treatment failure in a subset of 16% of the first episode and 14% of the multi-episode samples respectively. These results are consistent with the findings of Wiersma et al. [
54] who reported that on average 1 in 6 patients failed to recover from each of their first four relapses, irrespective of which relapse it was.