Plasma oxytocin changes and anti-obsessive response during serotonin reuptake inhibitor treatment: a placebo controlled study.

Humble MB, Uvnäs-Moberg K, Engström I, Bejerot S

BMC psychiatry23 Dec 2013Cited by 28 (Europe PMC)

PMID24359174PMCIDPMC3877985DOI10.1186/1471-244x-13-344PepBankPUB-24359174

Summary

BackgroundThe drug treatments of choice for obsessive-compulsive disorder (OCD) are serotonin reuptake inhibitors (SRIs). However, a correlation between the neuropeptide oxytocin in cerebrospinal fluid and the severity of OCD has previously been shown, and oxytocin and serotonin are interconnected within the brain. Few studies have investigated whether SRIs have any effect on oxytocin; thus, our aim was to explore the possibility that oxytocinergic mechanisms contribute to the anti-obsessive effect of SRIs.MethodIn a randomized, double-blind trial, comparing SRIs (clomipramine and paroxetine) with placebo in 36 adults with OCD (characterized for subtypes), plasma oxytocin was measured with radioimmunoassay after plasma extraction, at baseline, after 1 week, and after 4 weeks of treatment, and related to baseline severity and clinical response after 12 weeks, as measured by the Yale-Brown Obsessive Compulsive Scale (Y-BOCS).ResultsBaseline oxytocin levels correlated positively with baseline Y-BOCS ratings, but only among the future SRI responders. Patients with early onset of OCD had higher baseline oxytocin. During treatment, plasma oxytocin did not differ between SRI and placebo treatment. In SRI responders, plasma oxytocin first decreased and then increased; in non-responders (to SRI as well as to placebo), the reverse was the case. After 4 weeks, treatment responders had attained higher oxytocin levels compared to non-responders. The intra-individual range (i.e., the variability) of plasma oxytocin between measurements was the measure that best differentiated responders from non-responders. This range was higher in responders than non-responders, and lower in patients with autistic traits.ConclusionsSRIs have highly variable effects on plasma oxytocin between individuals. The associations between baseline oxytocin and OCD severity and between oxytocin changes and treatment response support the notions that oxytocin is involved in OCD pathophysiology, and that the anti-obsessive effects of SRIs are partly exerted through oxytocinergic mechanisms.

CC BYText from Europe PMC. Highlighted sentences are the source of results.

Results from this study7

No result from this study comes from a test of the peptide.

Natural levels measured7

These results measure the body's own peptide. Nobody was given the peptide. They are not evidence about taking it. They are left out of key results, evidence counts and charts.

01HumanEndogenous levelRandomized controlled trialOther
In adults with OCD, plasma oxytocin during treatment did not differ between SRI and placebo.
In plain wordsIn adults with OCD, the body's own oxytocin levels did not differ between SRI and placebo treatment.
Peptide
Oxytocin
Outcome
No significant changePlasma oxytocin during SRI versus placebo treatment
Study
n = 36
Comparator
Placebo
Outcome group
Endogenous peptide levels · Mental health and mood
Source sentences
Summary
During treatment, plasma oxytocin did not differ between SRI and placebo treatment.
1 context sentence(design, population, supporting numbers)
Summary · context
In a randomized, double-blind trial, comparing SRIs (clomipramine and paroxetine) with placebo in 36 adults with OCD
This result measures the body's own Oxytocin. Nobody was given the peptide. It is not evidence about taking it.
Show in the study text Report a problemFND-2435917403
02HumanEndogenous levelRandomized controlled trialOther
In adults with OCD, baseline plasma oxytocin correlated positively with baseline Y-BOCS ratings, only among future SRI responders.
In plain wordsIn adults with OCD, higher natural oxytocin at the start went with more severe symptoms, only in people who later responded to SRI treatment.
Peptide
Oxytocin
Outcome
Not applicableBaseline plasma oxytocin versus baseline Y-BOCS (future SRI responders)
Study
n: not reported in source
Outcome group
Endogenous peptide levels · Mental health and mood
Source sentences
Summary
Baseline oxytocin levels correlated positively with baseline Y-BOCS ratings, but only among the future SRI responders.
1 context sentence(design, population, supporting numbers)
Summary · context
In a randomized, double-blind trial, comparing SRIs (clomipramine and paroxetine) with placebo in 36 adults with OCD
This result measures the body's own Oxytocin. Nobody was given the peptide. It is not evidence about taking it.
Show in the study text Report a problemFND-2435917401
03HumanEndogenous levelRandomized controlled trialOther
In adults with OCD, patients with early onset of OCD had higher baseline plasma oxytocin.
In plain wordsIn adults with OCD, those whose OCD began early had higher natural oxytocin levels at baseline.
Peptide
Oxytocin
Outcome
IncreaseBaseline plasma oxytocin by age of OCD onset
Study
n: not reported in source
Outcome group
Endogenous peptide levels · Mental health and mood
Source sentences
Summary
Patients with early onset of OCD had higher baseline oxytocin.
1 context sentence(design, population, supporting numbers)
Summary · context
In a randomized, double-blind trial, comparing SRIs (clomipramine and paroxetine) with placebo in 36 adults with OCD
This result measures the body's own Oxytocin. Nobody was given the peptide. It is not evidence about taking it.
Show in the study text Report a problemFND-2435917402
04HumanEndogenous levelRandomized controlled trialOther
In adults with OCD, plasma oxytocin first decreased and then increased in SRI responders; in non-responders the reverse occurred.
In plain wordsIn adults with OCD, natural oxytocin levels moved in opposite patterns in responders and non-responders during treatment.
Peptide
Oxytocin
Outcome
MixedPlasma oxytocin time course in SRI responders and non-responders
Study
n: not reported in source
Outcome group
Endogenous peptide levels · Mental health and mood
Source sentences
Summary
In SRI responders, plasma oxytocin first decreased and then increased; in non-responders (to SRI as well as to placebo), the reverse was the case.
1 context sentence(design, population, supporting numbers)
Summary · context
In a randomized, double-blind trial, comparing SRIs (clomipramine and paroxetine) with placebo in 36 adults with OCD
This result measures the body's own Oxytocin. Nobody was given the peptide. It is not evidence about taking it.
Show in the study text Report a problemFND-2435917404
05HumanEndogenous levelRandomized controlled trialOther
In adults with OCD, treatment responders had higher plasma oxytocin than non-responders after 4 weeks.
In plain wordsIn adults with OCD, people who responded to treatment had higher natural oxytocin levels after 4 weeks than those who did not.
Peptide
Oxytocin
Outcome
IncreasePlasma oxytocin at 4 weeks, responders versus non-responders
Study
n: not reported in source
Comparator
Non-responders
Outcome group
Endogenous peptide levels · Mental health and mood
Source sentences
Summary
After 4 weeks, treatment responders had attained higher oxytocin levels compared to non-responders.
1 context sentence(design, population, supporting numbers)
Summary · context
In a randomized, double-blind trial, comparing SRIs (clomipramine and paroxetine) with placebo in 36 adults with OCD
This result measures the body's own Oxytocin. Nobody was given the peptide. It is not evidence about taking it.
Show in the study text Report a problemFND-2435917405
06HumanEndogenous levelRandomized controlled trialOther
In adults with OCD, the intra-individual range of plasma oxytocin was the measure that best differentiated responders from non-responders, and it was higher in responders.
In plain wordsIn adults with OCD, how much natural oxytocin varied between measurements was higher in responders and best told them from non-responders.
Peptide
Oxytocin
Outcome
IncreaseIntra-individual range of plasma oxytocin, responders versus non-responders
Study
n: not reported in source
Comparator
Non-responders
Outcome group
Endogenous peptide levels · Mental health and mood
Source sentences
Summary
The intra-individual range (i.e., the variability) of plasma oxytocin between measurements was the measure that best differentiated responders from non-responders. This range was higher in responders than non-responders, and lower in patients with autistic traits.
1 context sentence(design, population, supporting numbers)
Summary · context
In a randomized, double-blind trial, comparing SRIs (clomipramine and paroxetine) with placebo in 36 adults with OCD
This result measures the body's own Oxytocin. Nobody was given the peptide. It is not evidence about taking it.
Show in the study text Report a problemFND-2435917406
07HumanEndogenous levelRandomized controlled trialOther
In adults with OCD, the intra-individual range of plasma oxytocin was lower in patients with autistic traits.
In plain wordsIn adults with OCD, natural oxytocin varied less between measurements in people with autistic traits.
Peptide
Oxytocin
Outcome
DecreaseIntra-individual range of plasma oxytocin by autistic traits
Study
n: not reported in source
Outcome group
Endogenous peptide levels · Mental health and mood
Source sentences
Summary
This range was higher in responders than non-responders, and lower in patients with autistic traits.
1 context sentence(design, population, supporting numbers)
Summary · context
In a randomized, double-blind trial, comparing SRIs (clomipramine and paroxetine) with placebo in 36 adults with OCD
This result measures the body's own Oxytocin. Nobody was given the peptide. It is not evidence about taking it.
Show in the study text Report a problemFND-2435917407

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Version 2Current
11 Oct 2026, 01:30 UTC
Study results updated
Version 1
9 Oct 2026, 02:49 UTC
First added · source update from Europe PMC

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