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- SCN4B, once mostly linked to heart function, plays a key part in getting back drug-related memories during relapse.
- Higher HDAC5 levels lower SCN4B expression, weakening the recall of drug-associated cues in the hippocampus.
- Mice with lower SCN4B activity showed much less drug-seeking behavior when they were again in drug-cue places.
- Scientists suggest focusing on SCN4B and HDAC5 might lead to future ways to treat substance use disorder.
- These gene control methods may also have uses in treating PTSD, anxiety, and other mental problems linked to memory.
Drug relapse is a big challenge in getting over substance use disorder (SUD). Places, feelings, and other things often bring back strong cravings even after a long time without drugs. A new study shows that the SCN4B gene might control drug-linked memories that lead to relapse. This finding opens up new possibilities in addiction science. And it suggests that we might be able to control relapse by changing specific tiny pathways in the brain.
What Is Relapse and Why Does It Happen So Much in Substance Use Disorders (SUDs)?
Drug relapse means going back to using a substance after trying to stop. It happens a lot among people with substance use disorders. And people often see it as a lack of trying hard enough, instead of seeing it as a sign of a complex brain problem.
The National Institute on Drug Abuse says that the rate of relapse for substance use disorders is between 40% and 60%. This rate is like those for other long-term illnesses such as asthma and high blood pressure. This helps show that addiction is a long-term problem that needs ongoing care and help.
One main reason for relapse is that drug-related memories stay in the brain. These memories are not just stored; they have strong feelings tied to them. They are often clear and deep in the parts of the brain that handle rewards and memory.
Things linked to past drug use—like certain places, social settings, or feelings—can bring these deep memories back strongly. This causes intense cravings and a strong urge to seek drugs.
The issue is often not a thought-out choice but a learned response in the brain. Over time, the brain links certain things to the reward feelings caused by drug use. When someone meets those things again, the brain basically plays the memory over. This often bypasses thinking things through and pushes toward relapsing.
Drug-Associated Memories: The Brain’s Automatic Trigger
Drug-linked memories form a brain trap that can cause relapse long after drug use has stopped. These memories often have extra strong feelings tied to them because drugs take over the brain’s reward area, filling it with dopamine. This flood makes the link stronger between the thing (music, people, places) and the drug feeling.
In terms of how the brain is built, the hippocampus is key in putting these events into context. It links memories to specific places, smells, or even small things like background noise. The amygdala, known for its part in learning through feelings, makes these drug-linked memories even stronger. This makes them especially hard to stop or forget.
Studies have shown that these memories become more set with more drug use. And the setting where drugs are used often becomes tied to the good feelings. Over time, this pairing becomes an automatic system: the setting brings back the memory, the memory causes craving, and craving can lead to relapse.
This is why just staying away from triggers often doesn’t work for good. The memory is still there, and it stays powerful. It is ready to start up again the moment something similar comes up. For lasting recovery, scientists think we must look at how to weaken these memories or break their link to behavior.
Meet SCN4B: A Gene That Showed Up in an Unexpected Way
The SCN4B gene, mostly studied for its role in nerve cell activity and heart function, has shown up as an unexpected but key player in how addiction affects the brain. SCN4B makes a part of a voltage-gated sodium channel. This channel helps keep electrical signals stable inside nerve cells. This basic function affects bigger networks involved in thinking processes, including those that handle memory storage and recall.
In the brain, small changes in sodium channel function can alter how easily nerve cells “fire” and talk to each other across different areas. Specifically, SCN4B activity in the top part of the hippocampus—the center for memory linked to place—can affect how strongly the brain focuses on and brings back drug-linked moments from its mental records.
What is new about this finding is how specific it is. Instead of changing the brain widely, SCN4B seems to play a role right where addiction memories are recalled. When SCN4B activity goes up in these areas, it might act like a tiny spotlight. It brightens the memory of drug-related times and makes relapse more likely.
Earlier addiction research often looked at brain chemicals or big brain systems. SCN4B brings a new way of thinking about targeted small systems where specific genes have a large effect on complex behaviors like addiction relapse.
The Study: From Mice to Stopping Memory
A study showed SCN4B’s importance in addiction. In their test, researchers taught mice to link a specific place with getting drugs. This was like how people link places to drug use memories. After a time without drugs, the mice were put back in the same place but did not get drugs.
Mice that were not changed showed the expected strong drug-seeking behavior. They walked around, sniffed, or stayed in the place where they got drugs before. But mice that had lower SCN4B activity in the top part of their hippocampus acted very differently. They did not prefer the drug-linked place. And they did not show the usual drug-seeking actions.
To say it simply: the memory pushing them to seek drugs did not come up or have its usual pull.
This finding suggests that SCN4B directly helps recall drug-place links made before. Stopping its function seemed to break the animal’s learned memory loop. This offers deep insight into a possible way to prevent relapse at the very start—when memories are recalled.
HDAC5: The Gene Control Helper That Changes SCN4B
Epigenetics is the study of how gene activity can change without changing the actual DNA code. One of the most important findings from the 2025 study is the role of HDAC5, a type of histone deacetylase. Enzymes like HDAC5 control how genes are active by changing how DNA is wrapped around histones. They basically turn genes on or off based on what is happening in the cell.
In this study, HDAC5 was found to be increased in mice that did not relapse. More testing showed that HDAC5 lowered the activity of SCN4B in the top part of the hippocampus. When HDAC5 levels went up, SCN4B activity went down. This lowering reduced the mice’s ability to recall drug-place memories. This helped them stay strong against things that could trigger relapse.
This shows a system that can be controlled:
- Make HDAC5 more active
- Lower SCN4B gene activity
- Stop the recall of memories that cause relapse
- Lower the chance of seeking drugs
This finding goes beyond just seeing a link. It shows a process, creating the thinking and biological path that future treatments might focus on.
How They Work Together: HDAC5 + SCN4B and the Way to Change Behavior
Finding this gene link is valuable because it gives us a chance for new ways to treat addiction. If HDAC5 can control SCN4B, and SCN4B controls the recall of drug-linked memories, then scientists may have a system with two parts they can use to affect behavior.
This supports the importance of how tiny parts work together in relapse. And it also means it can be used on a larger scale. It is easier to think about medicines or gene treatments changing HDAC5 activity than completely changing someone’s memory. In other words, being able to control a gene that controls access to the memory—instead of wiping out the memory itself—is more ethical and more likely to be possible soon.
Drug companies might one day create substances that make HDAC5 more active. Therapists might also plan therapy sessions to happen when SCN4B activity is lowest because of medicine. This could make therapy work better.
Why This Matters: From Brain Paths to Possible Treatments
This new understanding of drug memory circuits changes how we see addiction. It is a problem with brain circuits, not just a bad habit or weakness. Targeting relapse with biology may change the way we treat things. It could lead to treatments made for each person, based on their genes. Prevention could start at the tiny molecular level.
Possible future uses include:
- Medicines that target how SCN4B is made or how it works
- Gene therapy to increase or lower the activity of HDAC5 pathways
- Medicine and talk therapy combined to change how memories are set again
- Timed plans to prevent relapse that match the molecular cycles of gene activity
And because memory is at the heart of many mental health issues, these findings may apply to problems with similar memory links.
Looking Wider: Memory’s Bigger Part in Mental Health
Substance use disorder is not the only problem defined by memory loops that make things worse. PTSD, strong fears (phobias), and even some types of long-lasting depression are kept going by memories that keep coming back unwanted. The brain replays them even though they hurt the person.
Understanding the SCN4B + HDAC5 system may offer a model for other treatments that target memory issues not related to substances. For example:
- PTSD flashbacks might be lessened by controlling similar pathways.
- Thoughts that won’t go away in OCD could be weakened by breaking the tiny memory signs they rely on.
- Feeling stuck on sad thoughts in depression might be eased by targeting memory control.
So, instead of looking at addiction on its own, it becomes a way to get to bigger brain science discoveries focused on controlling memory.
Possible Treatment Outcomes: Gene Therapy, Memory Control & More
While still new, this kind of research opens doors to real-world uses:
- Gene editing using tools like CRISPR to control how SCN4B is made
- Making small molecule blockers or helpers for HDAC5
- Temporary and reversible ways to lower memory activity
- Medical treatments made for each person based on their brain gene makeup
Imagine a future where people with a high chance of relapse get a biological treatment that controls SCN4B for a short time during triggering events. Or, during the first time without drugs, treatments based on HDAC5 help strengthen recovery by limiting access to dangerous memory circuits.
This idea is still just that—an idea. But it is now scientifically possible.
What We Don’t Know Yet: Animal Studies and Next Steps
Even though the results are exciting, it is important to stress that these findings come from studies on animals. Mice have memory systems that are similar to humans, but the human brain is much more complex. This means using these findings directly in people might be hard.
More studies are needed to:
- Confirm SCN4B’s role in human brain tissue
- Find out if changing HDAC5 is safe
- Understand the long-term effects of treatments that change gene activity
- Create specific ways to deliver gene control methods that don’t require surgery
Science is still many steps away from using this in treating people, but the plan is there for future research.
Thinking About Right and Wrong: Can We—and Should We—Lower Memories?
Targeting memory—especially to treat problems—brings up questions about what is right and wrong. Lowering the recall of addiction-linked memories might help recovery. But should similar methods be used widely for trauma, feeling sorry, or sadness?
Things to think about include:
- Who decides which memories are bad?
- Could these systems be misused to control people?
- Might we lose experiences that shaped us, both good and bad, by mistake?
In the end, ways to prevent relapse that involve lowering memory activity will need to think about not just how well they work and if they are safe, but also a person’s right to choose, getting their okay, and their mental self over time.
Relapse Isn’t a Failure—It’s a Brain Problem
As this science changes, how the public understands it must change too. Drug relapse does not happen because someone doesn’t try hard enough or is a bad person. It is a deep biological event linked to how memories are made, recalled, and tied to rewards. Genes like SCN4B and controllers like HDAC5 help us understand this complex issue.
This understanding leads to care that is kind, made for the individual, and based on science. By looking at drug relapse through the lens of brain science, we make people feel less judged and open doors for better, more respectful treatments.
The Future of Stopping Relapse Might Start With Genes
SCN4B and HDAC5 show a big change in how we might prevent substance relapse. It is not just through trying hard or changing behavior alone. It is by carefully adjusting the tiny switches that recall addiction memories. As studies move forward, the hope of keeping recovery going may depend on changing the very tools the brain uses to remember.
It is a hopeful future. It is built on the belief that while we cannot change the past, we might soon control how strongly it pulls on the present.
