Drug cues are a range of internally and externally generated signals that support continued substance intake in a person with a history of substance use. In an individual affected by substance addiction, the presence of these cues helps foster the drug cravings that reinforce an ongoing pattern of uncontrolled substance use. In a study scheduled for publication in 2014 in the journal Addiction Biology, a team of Chinese and American researchers sought to determine if the intensity of the response to drug cues helps predict whether a person recovering from heroin addiction will relapse.
All human beings naturally feel an urge to act in certain ways in response to specific moods, environments or situations. Some of these urges are registered consciously in the brain, while others operate at an unconscious level. A person with a history of substance use goes through a form of this process when exposed to drug cues. These cues, which can originate in the external environment or within the mind, either consciously or unconsciously increase that person’s desire to engage in substance consumption, especially in the immediate or near future. As a rule, cues for drug or alcohol intake are particular to the individual. However, generally recognized sources of these substance-using prompts include being in a physical location previously associated with drug or alcohol intake, associating with other drug or alcohol users, seeing paraphernalia associated with substance intake, experiencing either common day-to-day stress or unusually high levels of stress and experiencing emotional states previously linked to drug or alcohol use.
A person affected by substance dependence or substance addiction has a physical need to keep consuming alcohol, an illicit/illegal drug or a mind-altering medication. Upon entering treatment, that person must typically go through a detoxification process in which use of the substance in question ceases. In some cases, the detox process is followed by the establishment of medically and psychologically supported substance abstinence. In other cases (especially in the context of addiction to heroin or other opioid narcotics), detox is followed by the temporary or long-term use of a less dangerous replacement substance that allows the individual to avoid severe withdrawal symptoms and gain control over his or her substance intake. In either situation, relapse remains a constant possibility during recovery. This fact holds true because the urge for substance use does not simply fade away during the detoxification process, during subsequent phases of active treatment or after active treatment ends. Ongoing exposure to drug cues can substantially intensify substance urges at any stage of recovery.
In the study slated for publication in Addiction Biology, researchers from three Chinese universities and the University of Florida College of Medicine used a real-time imaging procedure called functional magnetic resonance imaging (fMRI) to examine the brains of people addicted to heroin and determine if drug cue sensitivity has an impact on relapse rates. All told, 69 people participated in the study. Forty-nine of these individuals were in recovery for heroin addiction and receiving maintenance doses of the opioid medication methadone as a primary treatment; the remaining 20 participants were unaffected by heroin addiction. The researchers took fMRI scans of the brains of both groups while exposing them to drug cues associated with heroin use. Three months later, they compared the drug cue responses of those recovering addicts who had relapsed back into heroin use to the responses of the recovering addicts who did not experience a relapse.
The researchers concluded that, compared to the participants not involved in heroin use, the heroin users who experienced a relapse and the heroin users who did not both experienced easily detectable changes in brain function after being exposed to heroin-related drug cues. When they compared the recovering addicts who relapsed directly to the recovering addicts who didn’t relapse, they concluded that those individuals who relapsed had particularly notable changes in the function of some key, addiction-related brain areas. The relapsed study participants were also substantially more susceptible to drug use urges brought about by exposure to heroin-specific drug cues.
The study’s authors note that the differences in drug cue responses in the relapsing and non-relapsing groups were actually quite small. Despite this fact, they believe that an increased level of response to such cues may help addiction specialists accurately predict which people recovering from heroin addiction have heightened relapse risks.