Examining the potential preventative effects of minocycline prescribed for acne on the incidence of severe mental illnesses: A historical cohort study

Association between doxycycline use and long-term functioning in patients with schizophrenia

IMPORTANCE AND OBJECTIVE

The brain-penetrant tetracycline antibiotics, minocycline and doxycycline, have been proposed as potential candidate drugs for treatment of schizophrenia, based on preclinical studies and clinical trials. A potential long-term beneficial effect of these antibiotics for schizophrenia patients has not been investigated. This study was designed to determine if redemption of doxycycline prescription in schizophrenia is associated with decreased incidence of disability pension, a proxy for long-term functioning.

DESIGN

We performed a population-based cohort study with data from schizophrenia patients available through the Danish registers. Survival analysis models with time-varying covariates were constructed to assess incidence rate ratios (IRR) of disability pension after exposure to doxycycline or a non-brain penetrant tetracycline, defined as at least one filled prescription. The analysis was adjusted for age, sex, calendar year, parental psychiatric status and educational level.

RESULTS

We used data from 11,157 individuals with schizophrenia (4,945 female and 6,212 male; average age 22.4 years old, standard deviation (std) 4.50). 718 of these were exposed to brain-penetrant doxycycline, and 1,498 individuals redeemed a prescription of one or more of the non-brain-penetrant tetracyclines. The average years at risk per person in this cohort was 4.9, and 2,901 individuals received disability pension in the follow-up period. There was a significantly lower incidence rate of disability pension in schizophrenia patients who had redeemed doxycycline compared to patients who did not redeem a prescription of any tetracycline antibiotics (Incidence rate ratio (IRR) 0.68; 95 % CI 0.56, 0.83). There was also a significant lower rate of disability pension in schizophrenia patients who redeemed doxycycline compared to individuals who redeemed a prescription of one of the non-brain penetrant tetracycline antibiotics (IRR 0.69 95 % CI 0.55, 0.87).

CONCLUSIONS

In this observational study, doxycycline exposure is associated with a reduced incidence of disability pension. These data support further studies on the potential long term neuroprotective effects of doxycycline and level of functioning in schizophrenia patients.

A Sex-Dependent Association Between Doxycycline Use and Development of Schizophrenia

BACKGROUND

Doxycycline and minocycline are brain-penetrant tetracycline antibiotics, which recently gained interest because of their immunomodulatory and neuroprotective properties. Observational studies have suggested that exposure to these drugs may decrease the risk to develop schizophrenia, but results are inconsistent. The aim of this study was to investigate the potential association between doxycycline use and later onset of schizophrenia.

DESIGN

We used data from 1 647 298 individuals born between 1980 and 2006 available through Danish population registers. 79 078 of those individuals were exposed to doxycycline, defined as redemption of at least 1 prescription. Survival analysis models stratified for sex with time-varying covariates were constructed to assess incidence rate ratios (IRRs) for schizophrenia (ICD-10 code F20.xx), with adjustment for age, calendar year, parental psychiatric status, and educational level.

RESULTS

In the non-stratified analysis, there was no association between doxycycline exposure and schizophrenia risk. However, men who redeemed doxycycline had a significantly lower incidence rate for schizophrenia onset compared to men that did not (IRR 0.70; 95% CI 0.57-0.86). By contrast, women had a significantly higher incidence rate for schizophrenia onset, compared to women that did not redeem doxycycline prescriptions (IRR 1.23; 95% CI 1.08, 1.40). The effects were not found for other tetracycline antibiotics (IRR 1.00; 95% CI 0.91, 1.09).

CONCLUSIONS

Doxycycline exposure is associated with a sex-dependent effect on schizophrenia risk. The next steps are replication of the results in independent well-characterized population cohorts, as well as preclinical studies to investigate sex-specific effects of doxycycline on biological mechanisms implicated in schizophrenia.

Doxycycline exposure during adolescence and future risk of non-affective psychosis and bipolar disorder: a total population cohort study

Doxycycline has been hypothesized to prevent development of severe mental illness (SMI) through the suppression of microglia, especially if administered during the intense synaptic pruning period of adolescence. However, results from register studies on potential benefits differ considerably. The aim of the present study was to determine whether doxycycline exposure during adolescence is associated with reduced SMI risk, and to investigate if a direct and specific causality is plausible. This is a Swedish national population register-based cohort study of all individuals born from 1993 to 1997, followed from the age of 13 until end of study at the end of 2016. The primary exposure was cumulative doxycycline prescription ≥3000 mg and outcomes were first diagnosis of non-affective psychosis (F20-F29) and first diagnosis of bipolar disorder (F30-F31). Causal effects were explored through Cox regressions with relevant covariates and secondary analyses of multilevel exposure and comparison to other antibiotics. We found no association between doxycycline exposure and risk of subsequent non-affective psychosis (adjusted hazard ratio (HR) 1.15, 95% CI 0.73-1.81, p = 0.541) and an increased risk of subsequent bipolar disorder (adjusted HR 1.95, 95% CI 1.49-2.55, p < 0.001). We do not believe the association between doxycycline and bipolar disorder is causal as similar associations were observed for other common antibiotics.

Synaptic Pruning in Schizophrenia: Does Minocycline Modulate Psychosocial Brain Development?

Recent studies suggest that the tetracycline antibiotic minocycline, or its cousins, hold therapeutic potential for affective and psychotic disorders. This is proposed on the basis of a direct effect on microglia-mediated frontocortical synaptic pruning (FSP) during adolescence, perhaps in genetically susceptible individuals harboring risk alleles in the complement component cascade that is involved in this normal process of CNS circuit refinement. In reviewing this field, it is argued that minocycline is actually probing and modulating a deeply evolved and intricate system wherein psychosocial stimuli sculpt the circuitry of the "social brain" underlying adult behavior and personality. Furthermore, this system can generate psychiatric morbidity that is not dependent on genetic variation. This view has important ramifications for understanding "pathologies" of human social behavior and cognition as well as providing long-sought potential mechanistic links between social experience and susceptibility to mental and physical disease.

Adjunctive minocycline for major mental disorders: A systematic review

OBJECTIVES

This meta-analysis of randomized controlled trials (RCTs) examined the efficacy and safety of minocycline for three major mental disorders: schizophrenia, bipolar disorder and major depressive disorder (MDD).

METHODS

A systematic literature search of major electronic databases was conducted. Meta-analysis of clinical efficacy as defined by the respective studies, all-cause discontinuation, adverse drug reactions (ADRs) with standardized mean difference (SMD) and risk ratios (RRs) and their 95% confidence intervals (CI) was conducted using random-effects model. Quality assessment was performed with the Jadad scale and Cochrane risk of bias.

RESULTS

Sixteen RCTs (n=1357) on minocycline (50-300 mg/day) for schizophrenia (13 RCTs, n=1196), bipolar depression (1 RCT, n=49), and MDD (2 RCTs, n=112) were analyzed separately by diagnosis. Twelve RCTs mentioned randomized allocation specifically; the weighted Jadad scores were 4.0. Adjunctive minocycline outperformed placebo in improving total psychopathology [SMD: -0.45 (95%CI: -0.73, -0.16), p=0.002; I²=77%], positive [SMD: -0.15 (95%CI: -0.28, -0.02), p=0.02; I²=0%], negative [SMD: -0.62 (95%CI: -0.95, -0.28), p=0.0003; I²=85%] and general psychopathology scores [SMD: -0.28 (95%CI: -0.53, -0.03), p=0.03; I²=59%] in schizophrenia. Minocycline showed no significant effect on depressive and manic symptoms in both bipolar depression and MDD. Minocycline caused significantly less headache (p=0.02, number-needed-to-harm=14, 95%CI=5-14) than placebo in schizophrenia. All-cause discontinuation and other ADRs were similar between minocycline and placebo in each diagnostic category.

CONCLUSION

In this meta-analysis, adjunctive minocycline appeared to be efficacious and safe for schizophrenia. However, the efficacy of adjunctive minocycline for bipolar depression or MDD could not be demonstrated.

REVIEW REGISTRATION

PROSPERO: CRD42018102483.