Nostalgia can be one helluva drug. Our favorite memories often appear more technicolored and vivid than the experiences themselves. Meanwhile, some of our greatest works of literature and art warn us not to get stuck in the past, otherwise we might lose our sense of the present and stop chasing the future.
Now, a new study suggests that heavy marijuana users are more susceptible to holding onto negative emotions linked to memories, according to Live Science. That behavioral trait is also found in those with depression, and some preliminary research has backed up that data, showing links between cannabis usage and depression.
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The study focused around a psychological phenomenon called “fading effect bias.” As scientists have observed, humans tend to hold on more tightly to memories with a positive association than those with a negative one. Think of it as a “psychological immune system” of sorts, the study’s lead author Daniel Pillersdorf, a University of Windsor in Ontario graduate student in psychology, told Live Science. That fading effect bias, however, is seen in those with no mental health conditions, and could be affected by those who use drugs.
In the new study, the researchers analyzed information from 46 heavy marijuana users — most of whom used the drug at least four times a week — and 51 people who didn’t use marijuana. The participants were asked to recall, and provide written descriptions of, three pleasant memories and three unpleasant memories from the past year. The participants were then asked to rate the intensity of emotion tied to those memories, on a scale of negative 10, meaning extremely unpleasant, to positive 10, or extremely pleasant. They rated their emotions both at the time the memory was made and at the current time. (Marijuana users were not under the influence at the time the researchers asked them the questions.)
The researchers found that both marijuana users and nonusers showed fading affect bias, but for marijuana users, the fading was a lot less.
Pillersdorg says that compared to nonusers, marijuana users were “less able…to shed that unpleasantness associated with their memories.” In addition, “They were hanging on to that unpleasant affect over time, much more.”
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The scientists also observed that marijuana users described life events with less specific details.
For example, when asked about a happy event in the past year, marijuana users were more likely to respond with general or broad answers, such as “I went on vacation,” rather than recalling a specific event or day, such as “I attended my college graduation.” This phenomenon is known as “overgeneral autobiographical memory,” and it’s also linked with depression, Pillersdorf said.
It’s important to remember that this study did not pinpoint why these marijuana users held onto more negative feelings and had overgeneralized autobiographical memories. Merely, the study pinpoints an association between the two. The study also has yet to be published in a peer-reviewed journal.