Negative affect, pain and sex: The role of endogenous opioids

Abstract

Opioid neurotransmission modulates pain and negative affect during psychological stress.To determine whether these effects differ between men and women, the opioid receptor antagonist naltrexone or placebo was administered double-blind to 21 men and 22 women before they completed 30 minutes of difficult mental arithmetic. To heighten negative affect, participants received seven moderately noxious electric shocks during the math task, which were believed to be contingent upon performance. Before and after the math task, participants rated pain intensity and unpleasantness while their left hand was immersed in 2 o C water for up to 4 minutes. Anxiety, discouragement and anger were also rated before, during and after the math task. Tolerance of cold-induced pain was greater in men, whereas discouragement during the math task was greater in women. Opioid blockade did not influence ratings of negative affect, which increased in line with the intensity and unpleasantness of shock-induced pain. The intensity and unpleasantness of cold-induced pain increased after the math task only in women administered naltrexone.Within the naltrexone condition, pain ratings increased most in the most discouraged subjects. However, this relationship was absent in placebo recipients, implying that the hyperalgesic effect of psychological distress was tempered by opioid release. Greater stress-evoked discouragement in women than men may explain why cold-induced pain increased after the math task only in women administered naltrexone.

Painful effects of auditory startle, forehead cooling and psychological stress in patients with fibromyalgia or rheumatoid arthritis

“…In healthy controls, each of the tasks employed in the present study was found to suppress an experimental source of pain [17,18]. Thus, the present findings imply failure of stress-related pain modulation processes in fibromyalgia, and also in distressed patients with rheumatoid arthritis.…”

“…Two minutes later, participants were asked to rate pain intensity and then began to solve computer-generated additions and subtractions presented on a computer screen [18]. Participants were given up to 5 s to answer easy problems (e.g., 6 + 8 -2) and up to 11 s to answer hard problems (e.g., 116 + 138 -12) before the next was presented.…”

“…To compare effects of distress on pain in fibromyalgia and rheumatoid arthritis, the mental arithmetic test had a forced failure rate of 75%. A similar task was found to evoke strong negative affect, together with endogenous opioid release and reductions in pain in the most discouraged participants [18]. In addition to inducing distress, noxious forehead cooling might alter clinical pain by effects on autonomic arousal and/or sensitized nociceptive pathways [17,19].…”

Stress-evoked opioid release inhibits pain in major depressive disorder

“…Addition and subtraction items varied across five levels of difficulty, and the difficulty of the problems was adjusted automatically to ensure a 75% failure rate across the 25 minutes of the task [20]. At the outset of the task subjects were told that the number of shocks that they would receive would depend on their performance.…”

“…In human research, µ-opioid receptor blockade antagonized stress-induced analgesia evoked by noxious electric shocks [47,48], immersion of a limb in ice-water [28,40], the perception of failure on a difficult cognitive task [2,3,20], a combat video shown to Vietnam veterans with post-traumatic stress disorder [38], and a first-time parachute jump [27]. Effects of µ-opioid receptor blockade on experimental pain are more variable [16,23,40], possibly because of individual differences in sensitivity to or release of opioid peptides.…”