An interventional study of Heat/Humidity Exposure Condition and Thermoneutral Condition in Depressed Mood, Young Adults and Heat Stress, sponsored by Hartford Hospital. Recruiting at 1 site in United States. Open to participants aged 18 Years to 25 Years. Per ClinicalTrials.gov, last updated 2026-10-29.
Sponsored by Hartford Hospital · Not applicable, Interventional, and Basic science
The goal of this clinical trial is to learn how hot indoor temperatures affect mood in young adults with depression, with or without anxiety. It will also explore whether the time of day the heat happens matters, and whether changes in sleep, thinking, and daily activity help explain the effect.
The main questions it aims to answer are:
Participants will take part for about four weeks. During that time, participants will:
BACKGROUND AND RATIONALE Rising ambient temperatures are associated with worsening mood outcomes, and young adults with depressive disorders may be particularly susceptible. The mechanisms underlying this association remain poorly characterized. Three candidate pathways are measurable and potentially modifiable: sleep-wake disturbance, impaired cognitive performance, and reduced physical activity. Establishing whether these pathways carry the effect of heat on mood would identify targets for intervention that do not require modifying the thermal environment itself, which is often less modifiable.
A central and under-examined question is whether the timing of heat exposure matters. Nocturnal heat is hypothesized to act principally through sleep disruption, whereas daytime heat may act through effects on activity, cognition, and direct thermal discomfort. Distinguishing these requires an experimental contrast in exposure timing rather than a comparison between heat and its absence. Alongside affective outcomes, the study examines anger, aggression, and prosocial versus antisocial behavior, domains with an established association with ambient heat but limited experimental characterization in clinical populations.
RELATIONSHIP TO COMPANION OBSERVATIONAL STUDY This trial is conducted alongside a companion observational study within the same research program, Heat Effects on Mental Health in Young Adults (HEAT-MIND Lab PART 1), in which young adults are monitored while in their home environments across the summer months without assignment of any exposure. The observational study characterizes naturally occurring heat exposure and its association with sleep, mood, cognition, and activity in real-world conditions; while the present trial establishes directionality under controlled exposure. The two studies share a subset of monitoring instrumentation and measurement definitions, supporting comparison between experimentally controlled and naturalistic findings. PART 1 involves no assignment of interventions by the investigators and is reported separately.
STUDY DESIGN AND EXPOSURE This is a randomized, counterbalanced crossover study in which each participant serves as their own control across two laboratory weekends separated by two weeks. The two conditions are matched for total heat exposure and differ only in its timing.
In the daytime-heat condition, ambient temperature is maintained at 32°C from 08:00 to 20:00 and at 22°C overnight. In the nighttime-heat condition, this schedule is reversed. Absolute humidity is held constant at approximately 13 g/m³ across both conditions and both temperatures. Temperature and humidity are monitored continuously throughout both laboratory weekends.
Because both conditions contain heat, this design does not include a thermoneutral control arm. The contrast of interest is the differential effect of heat timing, and the exposure-matched structure removes total thermal load as a competing explanation for observed differences between weekends.
CONTINUOUS MONITORING PERIOD Individual participation spans 28 days. Ecological momentary assessment and wearable monitoring run continuously across this entire period, including during both laboratory weekends, using the HEAT-MIND mobile application (Avicenna Research) in combination with wearable sensors. Continuous monitoring captures repeated assessment of mood, anxiety, anger and aggression, cognitive performance, daily sleep diaries, wrist actigraphy, heart rate, ambient light exposure, and ambient temperature and humidity in the participant's own environment. This design permits each laboratory weekend to be interpreted against the participant's own preceding and following real-world baseline rather than against a single pre-study assessment.
Pre-laboratory sleep schedules and dietary intake are not controlled. This is a deliberate design choice grounded in the translational aims of the study: the research question concerns how real-world heat exposure affects young adults with depression against the background of their usual routines. Pre- and post-laboratory home-monitoring data (e.g., sleep duration, timing, physical activity, and environmental exposures) will be incorporated as model covariates and in sensitivity analyses of within-participant differences between the two laboratory weekends.
LABORATORY PROCEDURES AND MEASUREMENT Laboratory weekends are conducted at the Yale Biobehavioral Sleep Laboratory at the Yale School of Nursing, with participants resident from Friday afternoon through Monday midday, spanning three nights.
Overnight sleep is assessed by 18-channel attended polysomnography, including electroencephalography, electrooculography, electromyography, electrocardiography, respiratory inductance plethysmography, and airflow and thermistor channels, with concurrent wrist actigraphy.
Separately, waking neurophysiology is assessed by high-density electroencephalography using a 128-lead saline cap, administered at multiple timepoints across each weekend. This approximately 30-minute protocol comprises resting-state recording as well as auditory and visual oddball paradigms, supporting assessment of hypofrontality and functional connectivity in the Default Mode and Salience networks under each thermal condition.
On the final night of each laboratory weekend, participants are awakened at 02:00 for a scheduled nocturnal assessment comprising an additional ecological momentary assessment battery while being monitored through polysomnographic electroencephalography. This procedure allows mood, cognitive performance, and hypofrontality to be characterized during nocturnal wakefulness under each thermal condition. Because it occurs on the final night of both weekends, the procedure is symmetric across conditions and does not differentially perturb one exposure relative to the other.
Personal peripheral and core temperature measurement is continuous. Core body temperature is measured using an ingestible telemetric capsule (e-Celsius), peripheral temperature by iButton sensors (6 locations), and ambient temperature and humidity by fixed and portable environmental monitors (Kestrel Drop and SwitchBot IP65). Under-covers temperature and humidity are also measured with an iButton while participants are in bed, characterizing the sleep microenvironment, which may diverge from room-level conditions. Continuous heart rate is collected in parallel and additionally serves as a validated surrogate for core temperature, providing continuity in the event of capsule failure or early voiding and permitting internal cross-validation between measured and estimated core temperature within the sample.
Behavioral and affective assessment during laboratory weekends includes a semi-structured qualitative interview conducted by a research assistant on the final morning. The qualitative component provides participant-reported context on the experience of each exposure condition.
Cognitive tasks and measurements of mood and depression severity are administered via ecological momentary assessment.
STANDARDIZATION OF THE LABORATORY ENVIRONMENT While the pre-laboratory period is intentionally naturalistic, the laboratory environment is tightly standardized and held consistent across a participant's two weekends. Meals are provided on a fixed schedule, with calorie-counted meals and snacks, post-meal photography to estimate consumption, and documentation of additional intake. Bedding, sleepwear, and room furnishings are standardized. Lighting practices are held constant across weekends, including consistent overhead lighting, yellow-shifted emergency lighting overnight, and consistent management of the common-area window during evening and overnight periods; bedrooms have no windows. Ambient light exposure is additionally measured continuously by wearable photometric sensors (ActLumus), permitting light conditions to be characterized analytically rather than assumed constant.
Because participants are studied in the same physical environment under the same schedule across both weekends, stable features of the setting are not expected to bias one exposure condition relative to the other.
SAFETY MONITORING The study is overseen by an independent Data Safety Monitoring Board. Physician coverage during laboratory weekends is divided by call type, with heat-related clinical questions directed to a sleep medicine physician and psychiatric questions directed to a psychiatrist. Participants undergo alcohol and substance use screening at the outset of each laboratory weekend; and hydration is assessed via urine refractometry both at the weekend's outset and twice daily throughout the weekend, with a rehydration protocol in place if dehydration is noted (urine specific gravity >1.020).
STAKEHOLDER INVOLVEMENT Young adults with lived experience of mood disorders contributed to protocol development. A nationally recruited group of lived experience experts will participate in developing multimedia materials communicating findings to peers.
290 studies on the registry are indexed under Consciousness Disorders; 109 are open to participants now.
This study's planned enrollment of 75 is above the median of 47 across 191 interventional studies indexed under Consciousness Disorders.
Browse Consciousness Disorders studies →Hartford Hospital is the lead sponsor of 105 studies on the registry; 20 are open to participants now.
Of its 14 completed or terminated interventional studies of FDA-regulated products, 5 (36%) have results posted.
Counted across the registry records on this site, refreshed daily.
Go through the criteria one by one — yes, no or not sure — and take the list to your doctor or the study team. Kept in this browser only.
Exclusion Criteria:
Underlined terms in the criteria open these too. Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Before you join, the study team explains what taking part involves — its purpose, what happens, the risks and possible benefits — and answers your questions, so you can decide freely. Consent is usually recorded on a form (the informed consent form, ICF) signed by you or, where the law allows, by someone legally authorised to decide for you.
You can keep asking questions during the study, you are told of new information that matters, and you can choose to leave at any time.
Informed consent
Before you join, the study team explains what taking part involves — its purpose, what happens, the risks and possible benefits — and answers your questions, so you can decide freely. Consent is usually recorded on a form (the informed consent form, ICF) signed by you or, where the law allows, by someone legally authorised to decide for you.
You can keep asking questions during the study, you are told of new information that matters, and you can choose to leave at any time.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Subjects exposed to thermoneutral conditions during the day on Saturday; followed by hot/humid conditions during the night on Saturday night; followed by thermoneutral conditions during the day on Sunday; followed by hot/humid conditions during the night on Sunday night.
Other: Heat/Humidity Exposure Condition · Other: Thermoneutral Condition
Subjects exposed to hot/humid conditions during the day on Saturday; followed by thermoneutral conditions during the night on Saturday night; followed by hot/humid conditions during the day on Sunday; followed by thermoneutral conditions during the night on Sunday night.
Other: Heat/Humidity Exposure Condition · Other: Thermoneutral Condition
* Ambient temperature within the laboratory is set to 32 degrees Celsius (\~90 F) * Ambient humidity is set to \~13g/m³
* Ambient temperature within the laboratory is set to 22 degrees Celsius (\~72 F) * Ambient humidity is set to maintain \~13g/m³
PANAS-10
EMA Mood 10 items 5-pt Likert Score: 10-50
Time frame: periprocedurally* measures collected during lab weekends (i.e. periprocedurally) ONLY - marked with " * "
POMS-8 [depression subscale of POMS-60]
EMA Depressed Mood 8 items 5-pt Likert Score: 0-32
Time frame: periprocedurally*
PHQ-9
EMA Depressed Mood 9 items 4-pt Likert Score: 0-27
Time frame: baseline, pre-intervention, periprocedurally
GAD-7
EMA Anxious Mood 7 items 4-pt Likert Score: 0-21
Time frame: baseline, pre-intervention, periprocedurally
Qualitative Experience
In-person interview
Time frame: immediately after intervention*
Sleep Self Assessment
Audio-diary
Time frame: pre-intervention, periprocedurally
Sleep Monitoring
i) Sleep Stages (times, duration) - est. from Heart Rate (BPM) + Movement. Stages = Light, Deep, REM ii) Time Asleep \& Time in Bed iii) Time Awake \& Restlessness
Time frame: pre-intervention, periprocedurally
18-channel attended polysomnography (PSG)
i) EEG (32-channel, 10-20 system) Sleep stage distribution: N1, N2, N3, REM (% and minutes per stage) Total Sleep Time (TST) Sleep Onset Latency (SOL) REM Latency Wake After Sleep Onset (WASO) Sleep Efficiency (TST / Time in Bed) Number of awakenings Arousal Index (EEG-defined arousals/hour, AASM criteria) Spontaneous (non-respiratory, non-limb) arousal count ii) EOG REM density iii) Submental EMG Atonia confirmation for REM staging Chin EMG tone, used jointly with EEG/EOG for arousal scoring iv) Bilateral anterior tibialis EMG Periodic Limb Movement Index (PLMI; events/hour) PLM Arousal Index (PLM events assoc. EEG arousal) v) ECG Heart Rate \& Variability across sleep stages vi) Nasal pressure + oronasal thermal airflow AHI vii) Thoracic + abdominal respiratory effort belt Obstructive vs. central, RERA → RDI viii) Pulse oximetry SpO2 nadir ODI, ≥3% or ≥4% threshold %TST \< 90% ix) Snore sensor * TST snoring x) Body position sensor T/pos (supine, lateral, prone) Pos-dependent AHI
Time frame: periprocedurally*
Actigraphy
i) Steps/day ii) Distance/day iii) Heart rate (BPM)
Time frame: pre-intervention, periprocedurally
Flanker Task
EMA i) Reaction Time (RT) Mean/median RT (ms) / trial type x Congruent v. Incongruent trials Flanker Effect (or interference effect) = RT(incongruent) - RT(congruent) ii) Accuracy % correct x Congruent v. Incongruent Accuracy Interference Effect = accuracy(congruent) - accuracy(incongruent)
Time frame: pre-intervention, periprocedurally
2-Back Task
EMA i) Hit Rate * correctly identified targets ii) Miss Rate * targets not identified iii) False Alarm Rate * non-target trials incorrectly identified as targets iv) Correct Rejection Rate * correctly identified non-targets v) d' (d-prime) z(hit rate) - z(false alarm rate) vi) c (criterion) or β (beta) response bias
Time frame: pre-intervention, periprocedurally
Body Temperature
i) Skin-surface (C/F) ii) Core (C/F) iii) Peripheral (C/F)
Time frame: pre-intervention, periprocedurally
Waking EEG [128-lead saline cap]
i) Beta-to-Theta Power Ratio - calculated from frontal scalp electrodes Beta = 13-30 Hz Theta = 4-7 Hz ii) Source-reconstructed lagged phase synchronization between Default Mode Network and Salience Network ROIs - computed per frequency band from 128-channel resting-state hdEEG (eyes-open and eyes-closed analyzed separately). iii) P300 (P3b) Event Related Potential Target-minus-standard P3b peak amplitude (microvolts) and latency (ms) within 250-500 ms post-stimulus at midline electrodes - from 128-channel hdEEG during auditory and visual oddball tasks
Time frame: periprocedurally*
DAR-2 [subset of DAR-5]
EMA 2 items 5-pt Likert Score: 2-10
Time frame: baseline, pre-intervention, periprocedurally
Plan to share: Yes — De-identified IPD from this study, together with data dictionaries and supporting documentation, will be deposited in the NIMH Data Archive (NDA). Shared data will include physiological measurements (core and peripheral temperature, heart rate), polysomnography and EEG-derived measures, actigraphy, environmental monitoring data, ecological momentary assessment responses, cognitive performance data, and clinical assessment scores. Direct identifiers and protected health information will be removed or aggregated prior to deposit. Analysis code will be shared via GitHub, and technical documentation - including detailed protocols, data dictionaries, standardized coding manuals, and quality-control procedures - will be posted on OSF.io.
Supporting information: Study protocol, Statistical analysis plan, Informed consent form, Analytic code
Time frame: Data will be submitted to the NIMH Data Archive on the standard NDA submission cycle during the award period, with data made available to qualified investigators within 12 months after initial publication of results. Analysis code and technical documentation will be posted to GitHub and OSF.io at the time of primary publication. Study data will be retained in institutional research data repositories for a minimum of 10 years.
Access criteria: Access to de-identified data in the NIMH Data Archive is administered by NDA. Qualified investigators must hold an NDA account and submit a Data Use Certification endorsed by their institution's signing official, subject to review by the NDA Data Access Committee. Approved users agree to NDA terms prohibiting attempts to re-identify participants and requiring appropriate data security. Analysis code on GitHub and technical documentation on OSF.io will be openly available without restriction.
Start is estimated for Oct 2026; primary completion for Sep 2030, 47 months later.
Of 89 non-industry interventional studies with no phase under Consciousness Disorders, half reached primary completion within 20 months of starting (the median), counting those still running; a quarter within 9 and three quarters within 52. This study's planned 47 months is above that.
Counting every sponsor, half of 94 studies reached it within 19 months; a quarter within 8 and three quarters within 52.
How these figures are worked out, and which studies are left out of them.
From the registry record's own update history. This site started tracking changes on Sep 25, 2026; for anything earlier, see the record history on ClinicalTrials.gov ↗
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