Individuals with a long history of regular substance use tend to be inconsistent in how they use information about negative consequences to guide their decisions. This inconsistency suggests a new explanation for why some people continue to use substances despite experiencing severe personal and financial costs. These findings were recently published in the journal Translational Psychiatry.
A primary feature of severe substance use is the tendency to keep using drugs or alcohol even when it leads to negative consequences. These negative consequences can include strained family relationships, financial debt, or significant health problems. To understand this behavior, scientists study how people evaluate the costs and benefits of their actions.
Deciding whether to use a substance involves comparing different potential costs. For example, a person might weigh the social costs of continuing to use against the costs of stopping, such as withdrawal symptoms or losing a social circle. This decision-making process often happens in complex environments that can change without warning.
“People who struggle with substance use often continue despite negative consequences (e.g., strained relationships, health issues, occupational problems), but we know relatively little about how they actually weigh and compare those costs when making decisions,” said Sonia G. Ruiz, a doctoral candidate in clinical psychology at Yale University.
“For example, how do they compare the strain on relationships that comes from using against the loneliness of stopping when their social circle still uses to decide which cost is ‘worth it’?” Ruiz explained. “Most research focuses on how people respond to rewards, or learn to avoid just one cost, in a context that doesn’t change. We wanted to test how people compare multiple potential costs in contexts that change.”
To fill this knowledge gap, the researchers designed an experiment to test how changing environments impact risky choices. They recruited 137 adults from New Haven County, Connecticut. This group was selected to represent a wide range of substance use histories. The scientists excluded individuals with psychotic disorders, bipolar disorder, or medical problems that could interfere with task comprehension.
The scientists interviewed each participant to determine their total years of regular substance use. Regular use was defined as using a substance three or more times a week. The researchers added up the years of regular use across various substances, including alcohol, cannabis, opioids, and stimulants.
This cumulative number served as the primary measure of substance use severity for the experiment. About 75 percent of the sample had engaged in regular use of at least one substance in their lifetime. Participants earned fifteen dollars an hour, plus a potential bonus of up to ten dollars based on their game performance.
Participants completed a specialized decision-making task on a computer. For each of the 200 rounds in the task, participants had to choose between a black card and a white card. Each card displayed a random dollar amount between one and five dollars, which represented a potential loss.
Behind the scenes, one card always had a higher probability of causing the participant to lose that money. If participants chose the incorrect card, they lost the dollar amount shown on the screen. If they chose the correct card, they successfully avoided a loss and lost zero dollars.
Participants were told to build a feeling for which card was safer based on past outcomes. They could monitor their overall performance via a green bar at the bottom of the screen. This bar tracked how much money the participant had lost cumulatively throughout the game.
The task was divided into two distinct environments to test different types of learning. In the stable environment, one card had a 75 percent chance of causing a loss for 100 rounds straight. Participants were not told when they were in a stable or volatile environment.
In the volatile environment, one card predicted a loss 80 percent of the time, while the other predicted a loss 20 percent of the time. These probabilities switched between the two cards every 25 rounds. This design tested how people react when reliable patterns suddenly break down.
To understand the thought process behind every choice, the researchers applied mathematical models to the participant data. These computational models estimate how people learn over time in uncertain situations. The models calculate how quickly people update their beliefs and how consistently they use learned information to pick the best option.
The researchers found that individuals with more years of regular substance use behaved differently than those with less use history. Specifically, these individuals were less likely to repeat a choice after successfully avoiding a loss. They tended to change their answers regardless of whether their previous choice resulted in a loss or a zero-dollar outcome.
“We expected to find that people with greater substance use severity were less sensitive to losses, as most prior research suggests,” Ruiz told PsyPost. “We found that they could learn from cost information, but that they didn’t consistently translate it into choices.”
“It’s less about an inability to learn, and more about something interfering with using that learning in the moment (which likely differs for each person),” Ruiz explained. “This nuance is actually super important because it gives us a window into intervention that can focus on helping people use the information they already have more consistently.”
The mathematical models provided evidence that these individuals had an underlying inconsistency in how they used value information. They did not show a complete lack of sensitivity to the negative costs. Instead, they failed to consistently apply what they learned about the probabilities and dollar amounts to guide their future choices.
“People with greater substance use severity learn about what is costly similarly to everyone else, but where they differ is in how they use that information when making a choice,” Ruiz noted. “Something gets in the way of consistently acting on what they’ve learned, so their choices can look random or inconsistent even when they understand the consequences.”
“This fits with what we often see in real life; people know what the costs are, but that knowledge doesn’t always consistently translate into their choices,” Ruiz said. The most noticeable inconsistency occurred during the stable portion of the task, where the rules stayed exactly the same, yet choices appeared more random.
When interpreting these findings, the researchers note the effects are relatively moderate. “The strength of the relationships we found between substance use and decision-making differences is consistent with other studies, but is modest so can only help explain part of the picture,” Ruiz said. “I would use these results to think conceptually about how decision-making works for a person and what might get in the way of using what they know to make choices.”
The authors also note several potential limitations and misinterpretations to avoid. “First, we can identify that information about costs isn’t being used consistently, but we can’t yet say why that is for a given person (e.g., it could depend on someone’s emotional state, the specific situation, or someone’s history),” Ruiz explained.
“Second, this study is a first step. Our sample is relatively small and the costs in our task were monetary rather than substance-related, so future work will need to replicate these findings in larger samples and with stimuli that are more relevant to decision-making situations people actually face,” Ruiz added.
The study also relied on a single measurement of substance use severity that combined past and current use into one total number. Because active use might affect the brain differently than past use, grouping everyone together could mask important differences. The authors caution against using these specific findings to make clinical predictions.
“Third, this study was not designed to predict individual behavior, so we can’t use these results to predict who might develop a substance use disorder or relapse,” Ruiz warned. “What we can use these results for is to help understand the underlying decision-making process.”
The researchers suggest that future tests could separate current users from past users to better understand how risky decision-making changes during recovery. Emotional distress or a lack of working memory, the brain’s ability to hold and process information in the short term, could also contribute to inconsistent decision-making.
“The immediate next step is incorporating rewards in our decision-making task, since real-world choices involve comparing costs and benefits at the same time,” Ruiz said. “We have a manuscript under review that addresses this.”
“In the longer term, I think exploring how people orient to decision-making situations (for example, is the situation fair? Will their choices even impact the outcome?) will be important for understanding why cost information sometimes is used to make choices and sometimes isn’t,” Ruiz concluded.
The study, “The relationship between regular substance use and cost comparisons in stable and volatile learning contexts,” was authored by Sonia G. Ruiz, Samuel Paskewitz, and Arielle Baskin-Sommers.
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