Prediction of lithium treatment response in bipolar depression using 5-HTT and 5-HT1A PET



Lithium, one of the few effective treatments for bipolar depression (BPD), has been hypothesized to work by enhancing serotonergic transmission. Despite preclinical evidence, it is unknown whether lithium acts via the serotonergic system. Here we examined the potential of serotonin transporter (5-HTT) or serotonin 1A receptor (5-HT1A) pre-treatment binding to predict lithium treatment response and remission. We hypothesized that lower pre-treatment 5-HTT and higher pre-treatment 5-HT1A binding would predict better clinical response. Additional analyses investigated group differences between BPD and healthy controls and the relationship between change in binding pre- to post-treatment and clinical response. Twenty-seven medication-free patients with BPD currently in a depressive episode received positron emission tomography (PET) scans using 5-HTT tracer [11C]DASB, a subset also received a PET scan using 5-HT1A tracer [11C]-CUMI-101 before and after 8 weeks of lithium monotherapy. Metabolite-corrected arterial input functions were used to estimate binding potential, proportional to receptor availability. Fourteen patients with BPD with both [11C]DASB and [11C]-CUMI-101 pre-treatment scans and 8 weeks of post-treatment clinical scores were included in the prediction analysis examining the potential of either pre-treatment 5-HTT or 5-HT1A or the combination of both to predict post-treatment clinical scores.


We found lower pre-treatment 5-HTT binding (p = 0.003) and lower 5-HT1A binding (p = 0.035) were both significantly associated with improved clinical response. Pre-treatment 5-HTT predicted remission with 71% accuracy (77% specificity, 60% sensitivity), while 5-HT1A binding was able to predict remission with 85% accuracy (87% sensitivity, 80% specificity). The combined prediction analysis using both 5-HTT and 5-HT1A was able to predict remission with 84.6% accuracy (87.5% specificity, 60% sensitivity). Additional analyses BPD and controls pre- or post-treatment, and the change in binding were not significant and unrelated to treatment response (p > 0.05).


Our findings suggest that while lithium may not act directly via 5-HTT or 5-HT1A to ameliorate depressive symptoms, pre-treatment binding may be a potential biomarker for successful treatment of BPD with lithium.

Clinical trial registration

PET and MRI Brain Imaging of Bipolar Disorder Identifier: NCT01880957; URL:

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bipolar depression


positron emission tomography


magnetic resonance imaging


serotonin transporter

5-HT1A :

serotonin-1A receptor


healthy volunteer


selective serotonin reuptake inhibitor


Columbia University Medical Center


Brookhaven National Laboratory


Yale University Medical Center


Stony Brook University


Diagnostic and Statistical Manual of Mental Disorders – version IV


Hamilton Depression Rating Scale – 24 Item


likelihood estimation in graphical analysis

V T :

distribution volume

f P :

free fraction in plasma


binding potential


Structured Clinical Interview for DSM-IV


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We would like to thank the study coordinators Kristin Kolb, Sunia Choudhury, Kalynn Gruenfelder, Robert Lopez, Meghan Leonhardt, and study nurse practitioners Sally South and Colleen Oliva. We would also like to thank the Yale PET Center for radiotracer synthesis, PET scanning, and blood analysis. Finally, we thank the Center for Understanding Biology using Imaging Technology (CUBIT) image analysts at SBU for their work in data importing, analysis, and quality control.

Availability of data and materials

The datasets used and/or analyzed during the current study are available from the corresponding author on reasonable request.


The National Institute of Mental Health provided funding for this study (R01MH090276, PI: Ramin Parsey, MD, PhD).

Author information




MA and EB have contributed to the acquisition, analysis, and interpretation of the data, the draft, revision and finalization of the manuscript. CD contributed to the design of the work, the acquisition and interpretation of the data, and the revision and finalization of the manuscript. XL and RTO contributed to the analysis and interpretation of the data, and the revision and finalization of the manuscript. LK, NV, GP, MG, and DH contributed to the design of the work, the acquisition and analysis of the data, and the revision and finalization of the manuscript. CH contributed to the interpretation and revision and finalization of the manuscript. RVP contributed to the conception and design of work, the acquisition and interpretation of the data, and the revision and finalization of the manuscript.

Corresponding author

Correspondence to Mala Ananth.

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This study was approved by the Institutional Review Boards of Columbia University Medical Center (CUMC), Brookhaven National Laboratory (BNL), Yale University Medical Center (Yale), and Stony Brook University (SBU). All participants provided written, informed consent. Recruitment occurred from March 2008 through June 2017.

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The authors declare that they have no competing interests.

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Mala R. Ananth and Elizabeth Bartlett are co-first author

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Ananth, M., Bartlett, E., DeLorenzo, C. et al. Prediction of lithium treatment response in bipolar depression using 5-HTT and 5-HT1A PET. Eur J Nucl Med Mol Imaging 47, 2417–2428 (2020).

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  • Bipolar depression
  • Lithium
  • Prediction
  • PET
  • Serotonin transporter
  • Serotonin-1A