Can Naltrexone Cause Depression or Other Mood Changes?

Naltrexone does not appear to cause clinical depression in most people who take it. Randomized controlled trials consistently show that standard-dose naltrexone does not worsen depressive symptoms compared with placebo, and some data suggest it may even improve them over time. That said, the drug does alter how the brain handles reward and motivation, and a minority of users report subtle emotional changes, from feeling flat to a vague sense of unease. Understanding why those experiences happen, and why they differ so much from person to person, requires looking at how naltrexone interacts with the brain’s opioid and dopamine systems.

What Controlled Trials Actually Find

The most direct evidence comes from a randomized controlled trial in people with opioid dependence that was specifically designed to answer this question. Participants who received naltrexone did not show worsening of depressive symptoms. In fact, there was a trend toward improvement over time compared with the control group, and people who stuck with naltrexone treatment reported fewer depressive symptoms than those who did not.¹ The researchers concluded that depression should not be considered a common side effect or a reason to avoid prescribing the drug.

A study of extended-release naltrexone in heroin-dependent patients told a similar story. While these patients started with significantly higher depression scores than healthy volunteers, their scores dropped after just two weeks on the medication.² A large multicentre trial of naltrexone for alcohol dependence likewise found no safety concerns related to mood.³

A pooled analysis of trials using the naltrexone-bupropion combination for weight management offered an additional data point. Depression was actually reported less often in the naltrexone-bupropion group (about 2%) than in the placebo group (about 3%). No completed suicides, suicide attempts, or preparatory acts were found in any treatment group.⁴ The combination did, however, modestly increase reports of anxiety and sleep disturbance, which is worth noting for anyone tracking their overall mood picture.

Why Some People Feel Emotionally Dulled

If the trials generally look reassuring, why do some naltrexone users describe feeling emotionally blunted, as though the color has been dialed down on everyday pleasures? The answer lies in how the drug interacts with the brain’s reward circuitry. Naltrexone blocks mu-opioid receptors, which sit on dopamine-producing neurons in a brain region called the ventral tegmental area. Blocking those receptors reduces the firing of dopamine neurons, which in turn dampens the release of dopamine in pathways responsible for motivation and drive.⁵ At clinically effective doses, naltrexone has been described as chronically down-regulating mesolimbic dopamine release.⁶

The practical result is not necessarily sadness, but rather a dampening of anticipatory pleasure. A well-designed study in healthy adults found that naltrexone reduced “wanting” ratings for rewarding stimuli without changing “liking” ratings. People on naltrexone still enjoyed things when they experienced them, but they felt less pull toward those things in advance.⁷ That distinction matters. Full-blown depression typically involves both reduced wanting and reduced liking, plus persistent low mood. What naltrexone more commonly produces, when it produces anything, is a narrower experience: less craving and less anticipatory drive, which some people interpret as emotional flatness.

The brain’s opioid system also has a second pathway relevant here. Mu-opioid receptors tend to promote feelings of well-being and reward, while kappa-opioid receptors are associated with aversive, dysphoric states.⁸ Naltrexone blocks both. In theory, blocking kappa receptors could reduce dysphoria, partially counterbalancing the loss of mu-mediated pleasure. How those two effects balance out in any given person may help explain why some individuals feel worse and others feel fine or even better on the medication.

Dysphoria in Former Opioid Users

The strongest reports of naltrexone-induced mood changes come from people with a history of opioid use. A small placebo-controlled crossover study of former opioid addicts who had been drug-free for anywhere from nine months to nearly four years found that two out of four participants reported mild but statistically significant dysphoria while taking naltrexone. A third subject dropped out with symptoms resembling opioid withdrawal.⁹ This is a tiny study and should be read with caution, but the finding makes mechanistic sense. Chronic opioid use reshapes the brain’s endogenous opioid system, and blocking whatever residual opioid tone remains could remove a baseline sense of comfort that most people would never notice losing.

The challenge is separating the drug’s effects from the underlying condition. An observational study comparing naltrexone-treated patients, opioid agonist-treated patients, and healthy volunteers found that both patient groups reported substantially more anhedonia and depression than healthy people. But there was no meaningful difference between the naltrexone and agonist groups.¹⁰ In other words, the elevated depression scores tracked with having an opioid use disorder, not with which medication someone was taking. People in recovery from addiction carry a high baseline risk for depression regardless of their treatment, and attributing low mood to naltrexone when it may reflect the underlying condition is a common interpretive trap.

Stress Hormones and Naltrexone

Naltrexone also activates the body’s stress-response system, at least temporarily. Opioid receptors help regulate the hypothalamic-pituitary-adrenal (HPA) axis, which governs the release of cortisol and related stress hormones. When you block those receptors, stress hormone output tends to rise. In healthy volunteers, oral naltrexone produced significant increases in both ACTH and cortisol compared with placebo.¹¹ The study also found that people with a family history of alcoholism showed an exaggerated version of this response, including decreased vigor ratings, suggesting they may be more sensitive to the mood effects of opioid blockade.

A separate study in alcoholic patients during early withdrawal found a similar pattern, though the cortisol response was blunted compared with healthy controls, potentially because the HPA axis was already dysregulated by chronic alcohol use.¹² These hormonal shifts are typically most pronounced early in treatment and tend to stabilize, but they help explain why the first weeks on naltrexone can feel more stressful than usual for some people.

How Naltrexone Changes Emotional Processing

Beyond broad mood categories like “depressed” or “anxious,” naltrexone appears to alter how the brain processes emotional information in subtler ways. A study in healthy adults found that naltrexone increased attention to emotional facial expressions, slowed the identification of sadness and fear, and decreased the perceived intensity of emotionally charged scenes.¹³ Interestingly, the researchers interpreted these effects as more consistent with the drug’s kappa-antagonist activity, which would lean anxiolytic rather than depressogenic. In plain terms, naltrexone seemed to turn down the volume on emotional reactions rather than making those reactions more negative.

This is worth thinking about if you are on naltrexone and find yourself feeling less emotionally reactive. A reduced arousal response to emotional scenes is not the same thing as depression, even though it can feel disorienting if you are used to stronger emotional responses. Some people may experience this as a welcome calm, especially if their emotional baseline was turbulent. Others may perceive it as numbness. Both reactions could stem from the same pharmacological effect.

Low-Dose Naltrexone and Mood

Low-dose naltrexone (LDN), typically in the range of 1 to 5 milligrams rather than the standard 50 milligrams, has attracted interest as a potential treatment for depression, particularly in people who have not responded fully to conventional antidepressants. The theory is that at low doses, naltrexone briefly blocks opioid receptors and then washes out, prompting the body to upregulate its own endorphin production. The evidence so far is mixed.

A small proof-of-concept trial tested LDN as an add-on in people whose depression had relapsed despite being on antidepressants. Depression scores on the MADRS scale improved significantly more in the LDN group than in the placebo group, though the study was small and the researchers cautioned that confirmation in larger trials was needed.¹⁴ A separate case report documented a fibromyalgia patient whose depression went into remission only after LDN successfully treated the underlying pain condition, suggesting that LDN’s mood benefits in some cases may be indirect, working through pain relief rather than a direct antidepressant effect.¹⁵

However, a larger randomized double-blind trial that tested LDN as an adjunct for major depressive disorder found no difference between LDN and placebo on the primary depression measure after 12 weeks.¹⁶ The bottom line on LDN and mood is that the evidence is early, the positive results come from small studies, and the one better-powered trial did not find benefit. LDN does not appear to worsen depression, but it is premature to call it a reliable treatment for it.

The Naltrexone-Bupropion Combination

Naltrexone combined with bupropion is marketed as a weight-management drug, and because it is prescribed to many people who also have mood concerns, its psychiatric safety profile matters. The pooled analysis mentioned earlier found that depression reports were actually lower in the combination group than in the placebo group. Overall depression-scale changes from baseline were trivially small in both groups, suggesting the combination neither worsened nor meaningfully improved clinical depression scores in the weight-loss population.⁴

A separate open-label pilot study tested the same combination specifically in overweight or obese people who also had major depressive disorder. Depression scores dropped substantially over 24 weeks, and the safety profile was consistent with the known side effects of both drugs individually, with nausea, constipation, headache, and insomnia being the most common complaints.¹⁷ This was not a placebo-controlled design, so the improvement cannot be attributed to the drugs with certainty, but the finding at least suggests the combination does not aggravate depression in people who already have it. The bupropion component likely deserves much of the credit for mood stabilization, since bupropion is itself an antidepressant.

Genetics and Individual Variation

One reason naltrexone’s mood effects vary so much across people may be genetic. Variations in the gene for the mu-opioid receptor (OPRM1) and the dopamine transporter gene (DAT1) have been shown to predict how well naltrexone works for reducing heavy drinking. In a randomized trial, specific combinations of OPRM1 and DAT1 variants were associated with significantly different treatment responses to naltrexone compared with placebo.¹⁸ While this study focused on drinking outcomes rather than mood per se, the same receptor systems that mediate naltrexone’s therapeutic effects also mediate its reward and emotional effects. If your genetic makeup means naltrexone hits your opioid and dopamine systems harder, you may be more likely to feel the emotional dampening as well.

Family history may also matter. As noted in the HPA axis research, people with a family history of alcoholism showed stronger stress-hormone responses to naltrexone and reported decreased vigor.¹¹ Pharmacogenomic testing to guide naltrexone prescribing is not yet routine, but the research hints at why two people on the same dose can have very different experiences.

What to Watch For in Practice

Clinical guidance acknowledges that dysphoria, depression, and anxiety are potential side effects that prescribers may overlook.¹⁹ That does not mean they are common, but it means they belong on the monitoring checklist, especially during the first few weeks when HPA axis activation is likely at its peak. If you are starting naltrexone, it is reasonable to keep track of your mood in a simple way: a daily one-line journal, a mood-tracking app, or even a weekly self-check-in where you honestly assess whether you feel more flat, anxious, or low than before starting.

The practical signals worth paying attention to include a persistent loss of interest in activities you normally enjoy, a sense that nothing feels rewarding even when objectively good things happen, increased irritability without an obvious cause, or a new pattern of sleep disturbance. Any of these could reflect naltrexone’s effect on opioid and dopamine signaling, but they could equally reflect the natural mood fluctuations that come with recovery from addiction, changes in alcohol or substance use patterns, or unrelated life stressors. Bringing a specific pattern to your prescriber, rather than a vague complaint of “feeling off,” makes it much easier to figure out whether a dose adjustment or medication change is warranted.

Anxiety and Sleep as Separate Tracks

While depression gets most of the attention, anxiety and sleep disruption deserve their own mention. The pooled naltrexone-bupropion data showed that anxiety was reported in about 5% of the treatment group versus 3% of the placebo group, and sleep disorders were reported in roughly 13% versus 8%.⁴ These are modest absolute differences, and the bupropion component is a known contributor to insomnia. But for naltrexone monotherapy, the signal for anxiety is weaker and less consistent across studies. The stress-hormone activation that comes with opioid blockade could plausibly produce some anxious feelings early on, but most trials have not flagged clinically significant anxiety as a common outcome.

Sleep trouble is worth distinguishing from mood trouble, even though poor sleep reliably worsens mood. If insomnia shows up shortly after starting naltrexone and you are not taking bupropion alongside it, the timing may be worth discussing with your prescriber. Sleep disruption that resolves within the first couple of weeks is typical as the body adjusts; disruption that persists may need a different approach.