Dayanna Barreto’s scientific contributions

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Publications (3)


Supplementary Material
  • Data
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March 2019

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31 Reads

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Dayanna Barreto

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Fig. 1. Trial profile. 
Fig. 2. HAM-D scores at baseline and seven days after dosing. Statistical analysis shows a significant difference between ayahuasca (squares) and placebo (circles) seven days after dosing ( p = 0.019). Between-group effect size is high (Cohen's d = 0.98). Values are (mean ± S.E.M.). HAM-D scores: mild depression (8-16), moderate (17-23), severe (⩾24). 
Fig. 3. MADRS scores as a function of time. Significant differences are observed between ayahuasca (squares) and placebo (circles) at D1 ( p = 0.04), D2 ( p = 0.04) and D7 ( p < 0.0001). Between groups effect sizes are high at all time points after dosing: D1 (Cohen's d = 0.84), D2 (Cohen's d = 0.84), and D7 (Cohen's d = 1.49). Values are (mean ± S.E.M.). MADRS scores: mild depression (11-19), moderate (20-34), severe (⩾35). *p < 0.05; ***p < 0.0001. 
Fig. 4. Response and remission rates as a function of time. Response (a) and remission (b) rates were high for both groups at D1 and D2. At D7, response rate was significantly higher for ayahuasca [OR 4.95 (95% CI 1.11-21.02); p = 0.04; NNT = 2.66], while remission rate showed a trend toward significance [OR 7.78 (95% CI 0.81-77.48); p = 0.054; NNT = 3.44]. 
Fig. 5. HRS subscales and MEQ30 factors during the dosing session. (a) Significantly higher scores in the ayahuasca group in five HRS subscales: perception ( p < 0.0001), somaesthesia ( p < 0.0001), cognition ( p < 0.0001), intensity ( p < 0.0001), and volition ( p = 0.0003). Only affect was not significantly different between groups ( p = 0.38). (b) Significantly higher MEQ30 scores in the ayahuasca group in the total MEQ30 score ( p = 0.004), and three of its factors: mystical ( p = 0.049), transcendence of time and space ( p = 0.0008), and ineffability ( p = 0.003), except for the positive mood ( p = 0.32). Values are expressed as a percentage of maximum possible score. 
Rapid antidepressant effects of the psychedelic ayahuasca in treatment-resistant depression: a randomized placebo-controlled trial

June 2018

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3,556 Reads

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675 Citations

Psychological Medicine

Background: Recent open-label trials show that psychedelics, such as ayahuasca, hold promise as fast-onset antidepressants in treatment-resistant depression. Methods: To test the antidepressant effects of ayahuasca, we conducted a parallel-arm, double-blind randomized placebo-controlled trial in 29 patients with treatment-resistant depression. Patients received a single dose of either ayahuasca or placebo. We assessed changes in depression severity with the Montgomery-Åsberg Depression Rating Scale (MADRS) and the Hamilton Depression Rating scale at baseline, and at 1 (D1), 2 (D2), and 7 (D7) days after dosing. Results: We observed significant antidepressant effects of ayahuasca when compared with placebo at all-time points. MADRS scores were significantly lower in the ayahuasca group compared with placebo at D1 and D2 (p = 0.04), and at D7 (p < 0.0001). Between-group effect sizes increased from D1 to D7 (D1: Cohen's d = 0.84; D2: Cohen's d = 0.84; D7: Cohen's d = 1.49). Response rates were high for both groups at D1 and D2, and significantly higher in the ayahuasca group at D7 (64% v. 27%; p = 0.04). Remission rate showed a trend toward significance at D7 (36% v. 7%, p = 0.054). Conclusions: To our knowledge, this is the first controlled trial to test a psychedelic substance in treatment-resistant depression. Overall, this study brings new evidence supporting the safety and therapeutic value of ayahuasca, dosed within an appropriate setting, to help treat depression. This study is registered at http://clinicaltrials.gov (NCT02914769).


A randomized placebo-controlled trial on the antidepressant effects of the psychedelic ayahuasca in treatment-resistant depression

August 2017

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121 Reads

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25 Citations

Recent open label trials show that psychedelics, such as ayahuasca, hold promise as fast-onset antidepressants in treatment-resistant depression. In order to further test the antidepressant effects of ayahuasca, we conducted a parallel-arm, double-blind randomized placebo-controlled trial in 29 patients with treatment-resistant depression. Patients received a single dose of either ayahuasca or placebo. Changes in depression severity were assessed with the Montgomery–Åsberg Depression Rating Scale (MADRS) and the Hamilton Depression Rating scale (HAM-D). Assessments were made at baseline, and at one (D1), two (D2) and seven (D7) days after dosing. We observed significant antidepressant effects of ayahuasca when compared to placebo at all timepoints. MADRS scores were significantly lower in the ayahuasca group compared to placebo (at D1 and D2: p=0.04; and at D7: p<0.0001). Between-group effect sizes increased from D1 to D7 (D1: Cohen’ s d=0.84; D2: Cohen’ s d=0.84; D7: Cohen’ s d=1.49). Response rates were high for both groups at D1 and D2, and significantly higher in the ayahuasca group at D7 (64% vs. 27%; p=0.04), while remission rate was marginally significant at D7 (36% vs. 7%, p=0.054). To our knowledge, this is the first controlled trial to test a psychedelic substance in treatment-resistant depression. Overall, this study brings new evidence supporting the safety and therapeutic value of ayahuasca, dosed within an appropriate setting, to help treat depression.

Citations (2)


... Traditional antidepressants are poorly efficacious, require chronic dosing for symptomatic relief, and frequently fail to result in complete remission of major depression. 1,2 Psychedelics have been shown to have rapid persistent antidepressant and anxiolytic effects in humans from only one or two doses, [3][4][5][6][7][8] and antidepressant-like effects in rats [9][10][11] and fruit flies. 12 The mechanism underlying these effects is not fully understood, but it is believed to involve increased neuroplasticity. ...

Reference:

A Single Administration of Psilocybin Persistently Rescues Cognitive Deficits Caused by Adolescent Chronic Restraint Stress Without Long-Term Changes in Synaptic Protein Gene Expression in a Rat Experimental System with Translational Relevance to Depression
A randomized placebo-controlled trial on the antidepressant effects of the psychedelic ayahuasca in treatment-resistant depression
  • Citing Preprint
  • August 2017

... In addition to misleading reports of data, there is the issue of poorly constructed double-blind studies. As demonstrated through the Good Friday Experiment, it is essential that researchers preserve the integrity of a double-blind study [65]. Additionally, it is extremely important that studies detail any issues with the preservation of their doubleblind study within their published articles. ...

Rapid antidepressant effects of the psychedelic ayahuasca in treatment-resistant depression: a randomized placebo-controlled trial

Psychological Medicine