Effects of chronic khat use on cardiovascular, adrenocortical, and psychological responses to stress in men and women

Abstract

Background: Khat is a psychostimulant plant widely used in Africa and its use has been growing rapidly in Europe and North America.

Objectives: We investigated effects of chronic khat (Catha edulis) use on cardiovascular, adrenocortical, and psychological responses to acute stress.

Methods: Chronic khat users and nonusers were compared on physiological measures and mood reports in a cross-sectional, mixed design. Measurements were conducted during 24-hour ambulatory monitoring and during a laboratory session. A total of 152 participants (58 women) were recruited by flyers posted around Sana'a University campus and the surrounding community in Sana'a, Yemen. Salivary cortisol and self-report measures were collected during a 24-hour ambulatory period prior to a lab testing session. In addition, blood pressures (BP), salivary cortisol, and mood measures were assessed during rest and in response to acute mental stress.

Results: Khat users exhibited enhanced evening and attenuated morning cortisol levels, reflecting a blunted diurnal pattern of adrenocortical activity compared to nonusers. Khat users reported greater negative affect during the ambulatory period and during the laboratory session. In addition, they exhibited attenuated BP responses to stress.

Conclusions and scientific significance: These novel results demonstrate altered adrenocortical activity and increased dysphoric mood among khat users. The extent to which these associations are due to effects of chronic khat use per se or instead reflect predisposing risk factors for khat use is yet to be determined.

FIGURE 1.

Mean positive affect (top figure), negative affect (middle figure), and physical symptoms (bottom figure) reported during the ambulatory assessment period. *Significant difference between khat users and nonusers (p < .01); **Significant changes across time in khat users but not in nonusers (p < .05).

FIGURE 2.

Mean positive affect (top figure), negative affect (middle figure), and physical symptoms (bottom figure) reported before and after performing the acute mental stressor during the laboratory session. *Significant difference between khat users and nonusers (p < .01); **Significant increases in response to stress in khat users but not in nonusers (p < .05).

FIGURE 3.

Mean cortisol concentration obtained during the ambulatory assessment period (top figure) and then before and after performing the acute mental stressor during the laboratory session (bottom figure). *Significant difference between khat users and nonusers (p < .05); **Khat users had higher cortisol levels than nonusers during early evening, but blunted cortisol levels in the morning (p < .01); ***Female nonusers had higher increases in cortisol levels from the evening to the morning compared to female khat users (p < .05).

FIGURE 4.

Mean systolic blood pressure (SBP), diastolic blood pressure (DBP), heart rate (HR), and rate pressure product (RPP) during baseline rest, during the acute mental stressor, and during rest recovery. The acute stressful challenge produced significant changes in all measures (ps < .01). **Nonusers had higher diastolic BP levels than khat users during stress period (p < .05). ^#Higher heart rate in female nonusers compared with male nonusers (p < .05), but no such difference was found in khat users.

FIGURE 5.

Scatterplots depicting the relationship between salivary cortisol, negative affect, and physical symptoms after the acute stressors in khat users and nonusers. In nonusers, cortisol levels consistently correlated with negative affect and physical symptoms (ps < .05). No such correlations were found in khat users.