Many common medications change your heart rate variability, sometimes significantly. Antidepressants, antipsychotics, ADHD stimulants, and drugs with anticholinergic properties tend to lower HRV, while beta-blockers generally raise it. If you track HRV with a wearable device and recently started or changed a medication, that alone could explain a shift in your numbers.
HRV reflects how well your autonomic nervous system balances its two branches: the sympathetic side (fight or flight) and the parasympathetic side (rest and recover). Medications that tip this balance in either direction will show up in your HRV readings. Here’s what the research says about the major drug classes.
Beta-Blockers Increase HRV
Beta-blockers are one of the few medication classes that consistently raise HRV. They work by blocking the effects of adrenaline on the heart, which slows heart rate and allows the parasympathetic nervous system to exert more influence. In patients with heart failure, those taking beta-blockers showed an RMSSD of 31.6 ms compared to 22.7 ms in those not taking them, a roughly 40% improvement in this key measure of parasympathetic activity.
This increase in HRV is considered one of the beneficial effects of beta-blockers, not a side effect. Higher parasympathetic tone is linked to better cardiovascular outcomes. If you’ve started a beta-blocker and notice your HRV trending upward, that’s the medication working as intended.
Antidepressants Lower HRV, but Not Equally
All major classes of antidepressants reduce HRV compared to people not taking them, but the degree varies substantially depending on which type you take. Data from the Irish Longitudinal Study on Ageing found a clear hierarchy: SSRIs had the smallest impact, tricyclic antidepressants (TCAs) had a larger effect, and SNRIs were associated with the lowest HRV measures of any antidepressant class studied.
SNRIs suppress both the low-frequency and high-frequency components of HRV, meaning they dampen both branches of the autonomic nervous system. TCAs similarly reduce high-frequency HRV, which reflects parasympathetic activity. SSRIs still lower HRV relative to people on no medication, but they preserve more autonomic function than the other two classes. For older adults in particular, the cardiovascular implications of SNRI use may be worth discussing with a prescriber, since age already reduces HRV on its own.
ADHD Stimulants Reduce Parasympathetic Tone
Stimulant medications like methylphenidate shift the autonomic balance toward sympathetic dominance. Studies show significant decreases in both RMSSD and the high-frequency power of HRV during treatment, both of which are markers of parasympathetic (vagal) activity. This makes physiological sense: stimulants increase heart rate and blood pressure, which is the sympathetic nervous system taking a larger role.
If you’re tracking HRV while taking a stimulant for ADHD, expect your baseline to sit lower than it otherwise would. The drop reflects a real change in autonomic balance, not just measurement noise. How much your HRV decreases will depend on your dose and individual physiology.
Anticholinergic Medications
Any drug with anticholinergic properties will reduce HRV, because these medications directly block the neurotransmitter that the parasympathetic nervous system uses to slow the heart. The stronger a drug’s anticholinergic effect, the greater the suppression. This matters because anticholinergic activity shows up in a surprisingly wide range of medications: certain antihistamines, bladder medications, older antidepressants (TCAs), some antipsychotics, and muscle relaxants.
Research confirms that when you look specifically at vagal (parasympathetic) HRV measures, anticholinergic burden is one of the strongest predictors of reduced readings. If you take multiple medications with even mild anticholinergic effects, the cumulative impact on HRV can be substantial.
Antipsychotics Vary Widely
Antipsychotics are not a single category when it comes to HRV. Clozapine produces the largest reductions, with significant drops in SDNN, RMSSD, and the percentage of successive heartbeat intervals that vary by more than 50 milliseconds. Olanzapine and aripiprazole also lower these measures noticeably within just two weeks of starting treatment. Ziprasidone and risperidone, by contrast, did not produce statistically significant HRV reductions in the same studies.
The difference largely comes down to how strongly each drug binds to receptors that affect the autonomic nervous system, particularly anticholinergic receptors. Clozapine has one of the strongest anticholinergic profiles of any antipsychotic, which explains why it hits HRV hardest.
Dose Matters
The effect of antipsychotics on HRV is dose-dependent. Research comparing patients on low, medium, and high doses found that those on the lowest doses (under 500 mg/day in chlorpromazine equivalents) had autonomic function that wasn’t significantly different from healthy controls. The high-dose group showed markedly lower HRV than both the medium and low-dose groups, with a clear linear relationship between dose and autonomic suppression.
Benzodiazepines Have a Mixed Effect
Benzodiazepines interact with HRV in a more nuanced way than most other drug classes. In elderly patients, the sympathetic nervous system tends to ramp up in stressful situations (like arriving at a hospital), which shows up as a spike in the ratio between low-frequency and high-frequency HRV. Both midazolam and diazepam prevented this sympathetic spike, essentially keeping the autonomic balance more stable under stress.
Diazepam also increased overall HRV power in both younger and older patients, an effect not commonly seen with other sedatives. This doesn’t mean benzodiazepines improve cardiovascular health. Rather, they appear to blunt the body’s stress response in ways that register on HRV readings, particularly in acute or short-term use.
Nicotine
Although not a prescription medication, nicotine is worth mentioning because so many people use it and track HRV simultaneously. Nicotine reduces parasympathetic activity, with a more pronounced effect in men. In one study, male participants saw their RMSSD drop from about 58.6 ms before nicotine exposure to 52.4 ms afterward, roughly a 10% decrease. Female participants showed a smaller, non-significant decline. If you vape or use nicotine pouches, your HRV readings on days you use nicotine will likely be lower.
How to Interpret Your HRV on Medication
The most important thing to understand is that medication-driven changes in HRV don’t necessarily mean something is wrong. Beta-blockers raise HRV as part of their therapeutic benefit. Antidepressants lower it as a side effect of how they work, but the mental health benefits may far outweigh the autonomic cost. Context matters more than the number itself.
If you track HRV daily, your most useful comparison is your own trend over time on the same medication and dose, not someone else’s numbers or a population average. Starting, stopping, or changing the dose of any medication listed above can shift your baseline for weeks. Give your body at least two to four weeks to stabilize before drawing conclusions from your readings.
For people taking multiple medications, the effects can stack. Someone on an SNRI and an antihistamine with anticholinergic properties, for example, may see a larger HRV reduction than either drug alone would produce. Keeping a log of medication changes alongside your HRV data makes it much easier to identify which drug is responsible for a shift.