A randomized, double-blind, placebo-controlled trial of quetiapine in the treatment of bipolar I or II depression
If quetiapine is being used for bipolar depression, is the lower 300 mg dose enough for me, since the trial found no added benefit at 600 mg?
Reasonable evidence with real limitations. how we score evidence
Caveat on this rating: Funding statement could not be read (paywalled); this BOLDER I registration trial supported the manufacturer's bipolar-depression indication, so sponsor involvement is plausible but unverified.
In 542 outpatients with bipolar I or II depression treated for 8 weeks, about 58% responded on quetiapine (300 or 600 mg/day) versus 36% on placebo, with 300 mg working as well as 600 mg.
Worth asking
If quetiapine is being used for bipolar depression, is the lower 300 mg dose enough for me, since the trial found no added benefit at 600 mg?
What it is FDA approved for
Read off the label. Trial duration and approval year are shown only where they were recorded — never inferred.
- Schizophrenia (adults; adolescents 13-17)
- Bipolar I disorder, acute manic episodes (monotherapy or adjunct to lithium/divalproex; ages 10-17 monotherapy)
- Bipolar disorder, acute depressive episodes (monotherapy) · trials ran 8-week randomized trials
- Bipolar I disorder, maintenance treatment (adjunct to lithium or divalproex)
- Major depressive disorder, adjunctive treatment with antidepressants (Seroquel XR only)
Source
A randomized, double-blind, placebo-controlled trial of quetiapine in the treatment of bipolar I or II depression — Calabrese JR, et al. (2005)
Top-tier peer-reviewed journal
Read the source: https://doi.org/10.1176/appi.ajp.162.7.1351
DOI: 10.1176/appi.ajp.162.7.1351
How this was scored
- Study design
- Randomised controlled trial
- Funding
- Funding not disclosed
- Published in
- Top-tier peer-reviewed journal
- Sample size
- 542
- Preregistered
- No
- Conflicts disclosed
- No
- Independent of proponent
- not recorded
- Retracted
- No
Read the full scoring rubric, including what it can't tell you.
Published August 19, 2026.
Questions
How strong is the evidence behind this?
Resolv rates this source "moderate evidence". Reasonable evidence with real limitations. It scores 64 out of 100 on our published rubric. One caveat travels with that badge: Funding statement could not be read (paywalled); this BOLDER I registration trial supported the manufacturer's bipolar-depression indication, so sponsor involvement is plausible but unverified. The score is calculated from recorded facts about the source — study design, funding, publication venue, sample size, preregistration — not typed in by an editor.
What is the source for this?
A randomized, double-blind, placebo-controlled trial of quetiapine in the treatment of bipolar I or II depression — Calabrese JR, et al. (2005). Published in: Top-tier peer-reviewed journal. DOI: 10.1176/appi.ajp.162.7.1351. The full source is linked on this page so you can read it yourself.
Who paid for this research, and does that matter?
Study design: Randomised controlled trial. Funding: Funding not disclosed. Independence from the proponent is not recorded. Industry sponsorship is one of the most reliably measured biases in medicine, which is why funding carries real weight in the score rather than sitting in a footnote.
Is quetiapine (Seroquel), seroquel FDA approved?
Yes — FDA approved for Schizophrenia (adults; adolescents 13-17), Bipolar I disorder, acute manic episodes (monotherapy or adjunct to lithium/divalproex; ages 10-17 monotherapy), Bipolar disorder, acute depressive episodes (monotherapy), Bipolar I disorder, maintenance treatment (adjunct to lithium or divalproex), Major depressive disorder, adjunctive treatment with antidepressants (Seroquel XR only). Approval is for a specific indication, not for everything the drug is prescribed for.
Is this medical advice?
This is information to bring to your prescriber, not medical advice and not a reason to change anything on your own. Nothing here is an instruction to stop or reduce a medication. If you are in crisis, call or text 988.
This is information to bring to your prescriber, not medical advice and not a reason to change anything on your own. Nothing here is an instruction to stop or reduce a medication. If you are in crisis, call or text 988.