ANXIETY
January 25, 2017

Alcohol’s Effects on Memory

Alcohol may make you unable to forget. And this matters for people with PTSD.

Some people drink to forget their fears. It's why alcohol is sometimes called “liquid courage.” But new research suggests that alcohol may also have the opposite effect: it may make it harder for us to let go of fear and the memories connected to it. This can be a significant problem for people with PTSD, many of whom use alcohol in an effort to self-medicate.

The brain has some complex tasks to execute with regard to memory: it has to remember the things that we want to remember and forget the things we want to forget, like unpleasant or traumatizing memories. Unfortunately, this isn’t always so easy, and it’s why bad memories can stay with us and lead to PTSD. But the new study suggests that alcohol may worsen this phenomenon, which is good to know in and of itself, but it may also suggest the way to future medications for PTSD.

“In fact, binge drinking or other attempts to use alcohol to self-medicate could be sabotaging any therapy efforts.”

To test how alcohol affects fear memories, researchers from Johns Hopkins University School of Medicine exposed rats to electric shocks to their feet via a special cage equipped with a metal floor grid. Rats freeze when they encounter a painful stimulus, so the researchers could measure their fear response by measuring their freeze behavior. They also paired a tone with the shock (sounding the tone slightly before the shock occurred), so that the rats learned to freeze in response to the tone alone.

Then the team gave the rats either water or water mixed with a little alcohol. Finally, they sounded the tone without the shock to try to “extinguish” the association between tone and shock.

Rats who’d had plain water were slightly less likely to respond to the tone by freezing than rats who’d had alcohol — 40% of the former group still froze, while 50% of the latter group did. And this suggests that alcohol may be interfering with the brain’s ability to adapt to the new and safer conditions once a threat is gone.

But the researchers took it a step further. They looked at the brains of the mice in both conditions, and found that in the mice given alcohol, there were more glutamate receptors at the synapses (the space between brain cells, through which they communicate), which they believe is responsible for the lingering fear response in these animals. Indeed, when the team used a drug to block these receptors from receiving signals, the fear responses of the mice given alcohol were significantly reduced – again, this group of mice froze about 40% of the time without the drug, but those given the drug froze only 20% of the time.

Rats responding to shocks and tones might seem a far cry from people dealing with traumatic events, but rats’ brains are surprisingly similar to human brains. They have often been studied to learn about how fear and stress function. The researchers believe the results will lead to new medications for people dealing with PTSD.

“If the effects of alcohol on memories to fearful responses are similar in humans to what we observe in mice, then it seems that our work helps us better understand how traumatic memories form and how to target better therapies for people in therapy for PTSD,” study author, Norman Haughey, said in a statement. “In fact, binge drinking or other attempts to use alcohol to self-medicate could be sabotaging any therapy efforts.”

There were more glutamate receptors at the synapses (the space between brain cells, through which they communicate) of the mice given alcohol, which the researchers believe is responsible for the lingering fear response in these animals.

A large percentage of people with PTSD use alcohol to try to calm themselves, which, according to these results, is probably doing more harm than good. And if those people are also taking prescription medications, like anti-anxiety medications, antidepressants or sleep aids, this may also affect the memory or extinction process in other ways.

One way to make therapies for PTSD more effective in the future might be to give a glutamate receptor blocking drug along with PTSD therapy. “It may be possible to improve the effectiveness of psychotherapy in people with PTSD by using glutamate receptor blockers during desensitization sessions when patients re-enact or remember the fearful situation,” says Haughey.

The team is planning to begin experiments with people to see if the results are applicable and if drugs might be effective. In the meantime, if you have PTSD or other painful memories you’re trying to forget, continue with your current therapy — and cut back on your alcohol use. It may be making the memories stronger instead of weaker.

The study is published in the journal Translational Psychiatry.

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