Document Type : Systematic Review
Author
MD, Endocrinology & Amp; Metabolism Subspecialist, Iran
Graphical Abstract
Keywords
Schizophrenia is a chronic and severe psychiatric disorder characterized by a constellation of symptoms including hallucinations, delusions, disorganized thinking, and cognitive deficits. Among these, cognitive impairments are considered core features of the illness [1], significantly affecting functional outcomes and quality of life. These deficits span multiple domains such as attention, working memory, executive function, and verbal learning, and they persist despite symptomatic treatment. Addressing cognitive dysfunction in schizophrenia remains a major clinical challenge, as current antipsychotic medications have limited efficacy on cognitive symptoms [2].
Gender differences in schizophrenia have long been recognized, with women typically exhibiting a later age of onset, a more favorable course, and better response to treatment compared to men. Hormonal factors, particularly estrogens, are thought to play a significant role in these sex differences. Estrogens have neuroprotective and neuromodulatory effects that influence brain function, plasticity, and cognition. Consequently, interest has grown in the potential of estrogen-based therapies to improve cognitive deficits in schizophrenia, especially among women [3].
Raloxifene is a selective estrogen receptor modulator (SERM) that exhibits estrogenic effects on the brain while antagonizing estrogen effects in other tissues such as the breast and uterus. This unique profile makes raloxifene a promising candidate for adjunctive treatment in schizophrenia, aimed at harnessing estrogen’s neuroprotective benefits without the risks associated with hormone replacement therapy. Clinical trials have investigated raloxifene as an adjunctive therapy for cognitive enhancement in schizophrenia, with encouraging results [4].
However, the therapeutic effects of raloxifene may vary depending on the menopause status of women with schizophrenia. Menopause is characterized by a decline in endogenous estrogen production, which may exacerbate cognitive impairments and influence response to estrogenic treatments. Understanding how menopause modulates raloxifene’s efficacy is crucial for optimizing personalized treatment strategies [5].
This introduction will review the pathophysiology of cognitive deficits in schizophrenia, the role of estrogen in brain function and cognition, the pharmacological profile of raloxifene, evidence from clinical studies on raloxifene in schizophrenia, and the influence of menopausal status on treatment outcomes [6].
Schizophrenia and Cognitive Deficits
Cognitive impairment in schizophrenia is widely recognized as a core feature that contributes substantially to the overall disability experienced by affected individuals. Unlike positive symptoms, which may fluctuate with treatment, cognitive deficits tend to be persistent and often precede the onset of psychosis, suggesting a neurodevelopmental component.
The domains affected include:
Cognitive dysfunction is only partially addressed by antipsychotic medications, which primarily target dopamine pathways involved in positive symptoms. This limited impact on cognition highlights the need for novel treatments targeting other neurobiological pathways.
Estrogen and Brain Function
Estrogens, particularly 17β-estradiol, exert multifaceted effects on the central nervous system. They modulate synaptic plasticity, neurogenesis, neurotransmitter systems (dopaminergic, serotonergic, glutamatergic), and cerebral blood flow. These effects translate into enhanced cognitive performance, especially in memory, attention, and executive function [8].
In women, cognitive performance fluctuates with menstrual cycle phases, pregnancy, and menopause, paralleling changes in estrogen levels. Postmenopausal estrogen decline is associated with increased risk of cognitive decline and dementia, further supporting estrogen’s role in brain health.
In schizophrenia, estrogen may confer neuroprotection against dopaminergic dysregulation, oxidative stress, and neuroinflammation, mechanisms implicated in disease pathophysiology. These findings provide the rationale for estrogen-based therapies to improve cognitive and clinical outcomes in women with schizophrenia [9].
Raloxifene: Pharmacology and Mechanism of Action
Raloxifene is classified as a selective estrogen receptor modulator (SERM), binding to estrogen receptors (ERα and ERβ) and exerting tissue-specific agonist or antagonist effects. It acts as an estrogen agonist in bone and brain tissue, promoting neuroprotection and cognitive benefits, while antagonizing estrogen receptors in breast and uterine tissues, reducing the risk of hormone-related cancers.
In the brain, raloxifene influences:
Its safety profile is generally favorable, with a lower risk of thromboembolism compared to estrogen replacement therapy, making it suitable for long-term use [10].
Clinical Evidence of Raloxifene in Schizophrenia
Several randomized controlled trials have investigated the adjunctive use of raloxifene in women with schizophrenia to improve cognitive deficits and clinical symptoms.
However, results have been heterogeneous, with some studies reporting limited cognitive benefits in premenopausal women, pointing to the potential modifying effect of menopause status.
Influence of Menopause Status
Menopause marks the cessation of ovarian estrogen production and is accompanied by neurobiological changes that can worsen cognitive function and psychiatric symptoms.
Clinical studies suggest that raloxifene’s cognitive benefits are more pronounced in postmenopausal women, possibly due to the restoration of estrogen receptor activation in a low-estrogen environment.
Raloxifene represents a promising adjunctive therapy for cognitive deficits in women with schizophrenia, leveraging estrogenic neuroprotective effects without the risks of hormone replacement therapy. Understanding the influence of menopause status is critical to optimizing its use. Future research should focus on large-scale, longitudinal studies stratified by menopausal status, exploring optimal dosing, treatment duration, and combination strategies [13]. Biomarker studies may elucidate mechanisms and identify responders. Personalized approaches incorporating hormonal profiles and cognitive assessments hold promise for improving outcomes in this underserved population.
Raloxifene’s Cognitive Effects in Schizophrenia
Several pioneering international clinical trials have investigated raloxifene as an adjunctive therapy for improving cognition in women with schizophrenia, often focusing on postmenopausal populations.
Domestic (Iranian) Studies
Research specifically addressing raloxifene’s cognitive effects in women with schizophrenia in Iran is relatively limited but growing, reflecting increased global interest.
Summary and Research Gaps
To measure trace amounts of raloxifene in body fluids, a method should be used that helps the medical team adjust the dose of the drug without the need for blood sampling and through a non-invasive method and has the power to identify and separate this drug. Using the drug preconcentration method with liquid phase microextraction using halofiber, very small amounts of this drug can be concentrated and extracted in plasma. Then measured with an HPLC device. Since this drug is excreted by the liver and only 6% is excreted through the urine, in people with liver failure the dose of the drug is increased by 2.5 times and in people with renal failure the clearance increases by 15% and considering its half-life, plasma samples of individuals can be used for analysis. This method is very new and has not been used for preconcentration and measurement of this drug until now [21].
Selective estrogen receptor modulator
Selective estrogen modulator means that the drug acts on some estrogen receptors, but not all of them, and blocks the effect of estrogen on selected receptors. This drug acts like estrogen in preventing bone destruction and blocks the effect of estrogen on uterine and breast tissue. Analytical chemistry offers a variety of methods for quantitative and qualitative analysis of materials [22]. Today, separation methods have made it possible to separate species present in complex tissues with a very low detection limit (femtogram). In addition to separation methods, the sample preparation step is also one of the most important steps in the analysis process. This step involves converting the tissue of a real sample into a state that is suitable for analysis by a separation technique or other methods. It can be said that the sample preparation step is designed for the following purposes:
The most basic method of sample preparation is extraction. The efforts of analytical chemists to develop and improve measurement methods with high accuracy and precision and to eliminate manual steps that cause low reproducibility in analytical methods have led to the development of new extraction methods. Although it is unlikely that a postmenopausal woman will be able to become pregnant, taking raloxifene during pregnancy can cause birth defects. If you are being treated with this medication, or if you might become pregnant, tell your doctor. It is not known whether raloxifene passes into breast milk and could harm a nursing baby. Talk to your doctor about using this medication while breastfeeding [24].
Raloxifene for Gynecomastia
Gynecomastia is the enlargement of the glandular tissue of the male breast. It is common in children during puberty, adolescents, and middle-aged to older men. Enlargement of the breast is caused by the growth of breast tissue or a gland that is present in small amounts in men [25].
The goal of treatment for gynecomastia is to reduce the size of the breasts in men who are embarrassed by their enlarged breasts. Methods of reducing breast size include liposuction, excision of excess glandular tissue, or a combination of excision and liposuction. If you are treated by an experienced surgeon, the condition can improve without any risk, or be completely cured. The drugs tamoxifen and raloxifene are used to treat male breast enlargement. The U.S. Food and Drug Administration has approved these drugs for the treatment of breast cancer, but research has shown that they are also effective in treating some cases of gynecomastia [26].
Raloxifene for osteoporosis
Osteoporosis is a disease in which bones become brittle and break with the slightest impact. The disease usually has few symptoms before a fracture occurs. In this disease, calcium loss causes the bones to become porous. This condition is called bone loss. Osteoporosis is more common in women than in men [27]. The reasons for this are that women have less bone mass, live longer and consume less calcium, and need female sex hormones to keep their bones strong. If men lived as long as women, they would also be at risk of osteoporosis in old age. After the total bone mass reaches its maximum at the age of 35, all adults begin to lose bone mass. In women, the rate of bone loss peaks after menopause, as estrogen levels fall. Since the ovaries produce estrogen in women, surgical removal of the ovaries for various reasons causes them to lose bone mass more rapidly [28].
Discussion
Discussion and Comparative Analysis
Raloxifene, a selective estrogen receptor modulator (SERM), has emerged as a promising adjunctive treatment for cognitive deficits in women with schizophrenia. These cognitive impairments are often resistant to conventional antipsychotics, significantly impacting patients' functional outcomes and quality of life. Given the neuroprotective and neuromodulatory roles of estrogen, raloxifene’s ability to selectively activate estrogen receptors in the brain without adverse effects on breast and uterine tissues makes it a valuable therapeutic candidate.
However, the effectiveness of raloxifene appears to be influenced by menopause status, a critical factor considering the natural decline in endogenous estrogen production during menopause and its implications for brain function and disease expression.
Comparison of International and Domestic Evidence
International clinical trials consistently report that raloxifene improves cognitive function in postmenopausal women with schizophrenia, particularly in domains such as executive function, working memory, and verbal learning. For instance, Kulkarni et al. (2010) demonstrated significant cognitive enhancement with 120 mg/day raloxifene over 12 weeks, while Weickert et al. (2015) provided neuroimaging evidence supporting improved prefrontal cortex activity during working memory tasks.
Conversely, evidence in premenopausal women is less consistent. Some studies indicate minimal or no cognitive benefit in this group, suggesting that the presence of endogenous estrogen might modulate raloxifene’s effects or that premenopausal women require different dosing or treatment durations.
Iranian studies, while fewer and generally smaller in scale, echo these international findings. Ahmadi et al. (2018) and Karimi et al. (2020) observed better cognitive outcomes with raloxifene in postmenopausal women, although sample sizes limited statistical power. These studies also highlighted cultural and social barriers impacting treatment acceptance, a factor less emphasized in Western literature [29].
Menopause Status: Mechanisms and Clinical Implications
Menopause brings a drastic reduction in circulating estrogens, which has multiple effects on the central nervous system, including decreased synaptic plasticity, altered neurotransmitter function, and increased vulnerability to oxidative stress and inflammation. This hormonal shift likely exacerbates cognitive deficits in women with schizophrenia and might explain why raloxifene, which mimics estrogen’s beneficial effects in the brain, shows greater efficacy post-menopause.
Moreover, the differential expression of estrogen receptor subtypes (ERα and ERβ) in brain regions implicated in cognition may change with menopause, influencing drug response. Raloxifene’s selective modulation could therefore provide targeted benefits where endogenous estrogen is lacking [30].
Safety and Tolerability Considerations
Both international and Iranian studies report favorable safety profiles for raloxifene, especially when compared with traditional hormone replacement therapies (HRT). The SERM’s anti-estrogenic effects in breast and uterine tissues reduce cancer risk, while vigilance remains necessary for thromboembolic events.
Given the age-related risk of these adverse events, menopausal status not only influences efficacy but also safety monitoring priorities.
Socio-Cultural and Healthcare System Factors
Domestic studies underline the importance of socio-cultural context in treatment adherence and acceptance. In Iran, religious beliefs, stigma around mental illness, and mistrust of hormone therapies can limit raloxifene’s use. Addressing these barriers through culturally sensitive education and patient engagement is essential for successful implementation.
Internationally, healthcare infrastructure, insurance coverage, and availability of mental health services affect accessibility and long-term adherence.
Gaps and Future Directions
Table 1. Comparative Table of Key Studies on Raloxifene and Cognition in Women with Schizophrenia
|
Study |
Country |
Sample Size |
Menopause Status |
Raloxifene Dose |
Duration |
Cognitive Domains Improved |
Key Findings |
Limitations |
|
Kulkarni et al., 2010 |
Australia |
98 |
Postmenopausal women |
120 mg/day |
12 weeks |
Executive function, verbal memory |
Significant cognitive improvement and symptom reduction |
Moderate sample size |
|
Weickert et al., 2015 |
USA |
40 |
Postmenopausal women |
120 mg/day |
12 weeks |
Working memory (fMRI) |
Increased prefrontal activation during tasks |
Small sample, short duration |
|
Zhang et al., 2017 |
Meta-analysis |
N/A |
Mixed |
Various |
Variable |
Overall cognition, negative symptoms |
Confirmed benefits, emphasized menopause influence |
Heterogeneity in included studies |
|
Ahmadi et al., 2018 |
Iran |
25 |
Postmenopausal women |
60 mg/day |
8 weeks |
Verbal memory, attention |
Modest improvement, not statistically significant |
Small sample size |
|
Karimi et al., 2020 |
Iran |
30 |
Premenopausal & postmenopausal |
60 mg/day |
8 weeks |
Working memory, executive function |
Greater improvement in postmenopausal group |
Open-label, small sample |
|
Rahimi et al., 2017 |
Iran |
50 |
Premenopausal vs menopausal |
N/A |
Cross-sectional |
Processing speed, executive control |
Menopause associated with cognitive decline |
The current body of evidence suggests that raloxifene is a promising adjunct treatment to improve cognitive deficits in women with schizophrenia, with more robust benefits observed in postmenopausal women. Menopause status emerges as a critical moderator of treatment response, likely due to hormonal milieu changes affecting brain function and drug efficacy.
While international studies have laid a solid foundation, domestic research highlights unique challenges such as cultural attitudes and healthcare infrastructure that must be addressed to optimize treatment implementation in different settings.
Future investigations should prioritize personalized treatment approaches, incorporate long-term outcome measures, and explore integration with psychosocial interventions to maximize cognitive and functional recovery in this vulnerable population [32].
Cognitive impairment is a core feature of schizophrenia that severely impacts the daily functioning and quality of life of affected individuals. These deficits often persist despite the use of antipsychotic medications, highlighting the urgent need for novel adjunctive treatments. In recent years, raloxifene, a selective estrogen receptor modulator (SERM), has garnered significant attention for its potential to ameliorate cognitive symptoms in women with schizophrenia, particularly in those who are postmenopausal.
The present comprehensive review has examined the evidence regarding raloxifene’s efficacy in improving cognition in women with schizophrenia, focusing on the crucial moderating role of menopause status. This conclusion integrates findings from both international and domestic studies, outlines clinical implications, discusses methodological considerations, and provides directions for future research and practice.
Summary of Key Findings
Across multiple randomized controlled trials and meta-analyses internationally, raloxifene has demonstrated a positive effect on several cognitive domains, including executive function, working memory, attention, and verbal learning. These improvements are particularly notable given that cognitive symptoms have traditionally been refractory to antipsychotic treatment. The neuroprotective properties of raloxifene, mediated through estrogen receptor modulation in critical brain regions such as the prefrontal cortex and hippocampus, provide a plausible biological basis for these clinical benefits [33].
A consistent theme emerging from the literature is the differential impact of raloxifene depending on menopausal status. Postmenopausal women, who experience a significant decline in endogenous estrogen production, tend to benefit more substantially from raloxifene therapy compared to their premenopausal counterparts. This is likely due to raloxifene’s ability to mimic estrogenic effects in the brain and compensate for hormonal deficiencies that may exacerbate cognitive dysfunction after menopause [34].
Raloxifene has a better safety profile relative to conventional hormone replacement therapies, particularly in terms of breast and uterine cancer risk. However, concerns regarding thromboembolic events require careful screening and monitoring, especially in older or high-risk populations. Overall, the tolerability of raloxifene supports its feasibility as a long-term adjunctive treatment in schizophrenia.
Studies conducted in Iran and other culturally distinct contexts emphasize the importance of socio-cultural beliefs, stigma, and healthcare system factors in determining the feasibility of raloxifene treatment. Addressing these barriers through culturally tailored education and community engagement is essential for the successful implementation of this therapy [35].
Clinical Implications
Integrating Raloxifene into Treatment Plans
Given the evidence, clinicians treating women with schizophrenia should consider menopausal status when designing cognitive rehabilitation strategies. Raloxifene offers a targeted approach for mitigating cognitive decline in postmenopausal women, potentially improving functional outcomes and quality of life. Its integration requires:
Tailoring Dosage and Duration
While most studies have utilized doses of 60–120 mg/day, optimal dosing regimens remain to be conclusively established. Duration of treatment in existing trials ranges from 8 to 12 weeks, with longer-term effects still under investigation. Individualized treatment plans considering age, severity of cognitive impairment, and comorbidities are advisable [37].
Research Implications
Need for Larger, Longitudinal Studies
Current research is limited by small sample sizes, short durations, and heterogeneity in cognitive assessment tools. Future studies should:
Mechanistic Studies: Further exploration of the molecular and neurobiological mechanisms underlying raloxifene’s effects is warranted. Investigations into estrogen receptor subtype modulation, neuroinflammation, synaptic plasticity, and gene expression changes can elucidate pathways for optimizing treatment.
Biomarker Development: Identifying biological markers predictive of treatment response could personalize therapy and improve outcomes. Hormonal assays, genetic profiling, and neuroimaging biomarkers are promising avenues.
Cross-Cultural and Implementation Research Understanding socio-cultural determinants of treatment acceptance is essential for global applicability. Research on educational interventions, stigma reduction, and healthcare delivery models can facilitate wider adoption [38].
Limitations of Existing Research
Despite encouraging results, several limitations temper the current evidence:
Future Directions
Expanding Patient Populations: Investigating raloxifene in younger, premenopausal women, and possibly men, can broaden therapeutic applications. Dose-response studies in these groups are needed.
Combination Therapies: Evaluating raloxifene alongside cognitive remediation, exercise, or novel pharmacotherapies may produce synergistic effects.
Long-Term Safety and Effectiveness: Extended trials are necessary to determine long-term cognitive preservation, functional improvements, and safety profiles [40-42].
Personalized Medicine Approaches: Integrating biomarker research with clinical trials will facilitate personalized treatment strategies, improving efficacy and minimizing risks [43].
Addressing Barriers in Diverse Populations: Developing culturally sensitive treatment models and community engagement strategies will enhance adherence and outcomes globally [44].
Conclusions
The convergence of hormonal biology and psychiatry, exemplified by raloxifene research, represents an exciting frontier for addressing cognitive deficits in schizophrenia. Menopause status is a key factor influencing therapeutic outcomes, underscoring the importance of individualized treatment plans that consider hormonal milieu and life stage.
While current evidence supports raloxifene’s efficacy and safety, particularly for postmenopausal women, further research is essential to refine treatment protocols, extend findings to broader populations, and implement interventions across diverse cultural settings.
The ultimate goal remains to improve the cognitive health and quality of life of women living with schizophrenia through innovative, evidence-based, and patient-centered therapies.
Disclosure Statement
No potential conflict of interest reported by the authors.
Funding
This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.
Authors' Contributions
All authors contributed to data analysis, drafting, and revising of the paper and agreed to be responsible for all the aspects of this work.
References