Several studies have found gender-related differences in the epidemiology, clinical presentation, clinical course and response to treatment of schizophrenic disorder(1,2). Findings relating to a lower frequency of schizophrenia in women, its later onset and less severe clinical course(3,4), have led to the appearance of the "estrogen hypothesis" of schizophrenia, which postulates that estrogen has a protective effect in women susceptible to this disease(5).
The estrogen hypothesis in relation to schizophrenia is based on several studies that showed that estrogen levels are significantly lower in schizophrenic women than in healthy women,(6) and that outbreaks or onset of the disease tend to coincide with stages of the menstrual cycle in which estrogen levels are the lowest(7,8).
Studies on experimental animals have shown that estrogen has a modulating effect on the brain dopaminergic system(9,10) and that it also affects serotoninergic activity(11). Estrogens also enhance neuronal regeneration and block mechanisms of neuronal death(12).
The discovery that estrogen has a modulatory effect on the dopaminergic system has encouraged some researchers to study the therapeutic use of estrogen in schizophrenic patients. Several double-blind clinical trials have shown that estrogens are effective at improving psychotic symptoms(13-15). These last studies analyzed the efficacy of estrogens after one and two months, and mainly in relation to positive symptoms, in patients with the acute illness. However, in older patients it is the severity of the negative, rather than the positive, symptoms that seems to be associated with a poorer cognitive and social function. Moreover, positive symptoms tend to be less severe with age, while negative symptoms tend to persist(16).
Regarding the possible use of estrogens to treat post-menopausal women with schizophrenia, Lindamer et al.,(17) studied the psychopathology of menopausal patients with schizophrenia and found that patients in hormone replacement therapy required lower doses of antipsychotic drugs and presented less negative symptoms, whereas no differences were found in response to treatment in relation to positive symptoms.
The greater frequency of later onset schizophrenia in women than in men seems to be related to the drop in estrogen levels that occurs during the menopause. Häfner et al.(19) found that schizophrenia of late onset was more severe in women than in men, especially in relation to negative symptoms, and these results also appear to support the hypothesis that estrogens act as a protective factor before the menopause.
The use of estrogens as adjuvant therapy in schizophrenia seems promising, although in long-term treatment it can have a potentially negative effect on breast and uterine tissue(20,21). This was the reason we chose raloxifene for our study, which is a selective estrogen receptor modulator (SERM) that can act as a tissue-selective agonist or antagonist. Raloxifene is a first-generation SERM used in the preventive treatment of post-menopausal osteoporosis and does not affect breast or ovarian tissue. (22). It has agonistic effects on the brain(23). Raloxifene seems to influence multiple neurotransmission pathways, including that of seratonin in the frontal cortex, basal and striated ganglia(24), areas of the brain that are commonly affected in schizophrenic patients.
There is some evidence that raloxifene can be useful in the treatment of some mental disorders in post-menopausal women(25,26). Recently, Kulkarni et al.(27) have reported preliminary data that also seem to support a role for raloxifene in schizophrenic patients.
Our team conducted a 12-week, randomized, double-blind, placebo-controlled clinical trial funded by the Stanley Foundation, to assess the value of 60 mg of raloxifene as adjuvant treatment for the negative symptoms, and other psychotic symptoms, in post-menopausal women. In our study on 33 patients, we found that women in the raloxifene group showed a greater improvement in both positive and negative symptoms, and also in general psychopathological symptoms, than women who had only received antipsychotic medication(28).
Since part of Raloxifene's mechanism of action involves activating the estrogenic receptors, some studies have explored the possibility that polymorphisms in these alfa (ESR1) or beta (ESR2) estrogenic receptor genes can modify the effects of treatment with raloxifene(29-31). Several pharmacogenomic studies have reported that single nucleotide polymorphisms (SNPs) in these genes, affect raloxifene treatment in relation to its endothelial function(29), cholesterol levels(30) and bone mineral density(31). Nevertheless, no studies have assessed whether these SNPs of ESR1 or ESR2 can influence raloxifene's effects in the brain. Based on the positive results of our preliminary study, we have designed a longer clinical trial with the same dose of raloxifene that had been effective in the first study. We aim to include in this 6-month placebo-controlled, randomized, double-blind clinical trial a larger number of post-menopausal women with schizophrenia, and improve the clinical assessments by using a larger battery of psychometric tests in areas of social functioning and neuropsychological performance. Genotypic studies will be conducted of the 4 SNPs in the ESR1 (rs9340799, rs2234693, rs1801132) and ESR2 (rs1256049) genes, to control the effects of patients' genotypes on response to treatment.
DESCRIPTION OF THE TARGET POPULATION
The sample includes post-menopausal women diagnosed with schizophrenia according to DSM-IV-TR criteria.
Post-menopause is defined as 1) aged over 45 years with a minimum of one year of amenorrhea and FSH levels higher than 20 UI/L or 2) aged over 50 years old with at least one year of amenorrhea.
