Physiological and affective reactivity to a 35% CO2 inhalation challenge in individuals differing in the 5-HTTLPR genotype and trait neuroticism.

The inhalation of 35% carbon dioxide (CO2) results in an acute stress response in healthy individuals and may accordingly provide a good paradigm to examine potential vulnerability factors for stress reactivity and stress-related psychopathology. It has been proposed that CO2 reactivity is moderated by genetic (5-HTTLPR) and personality (neuroticism) factors, yet no experimental study has investigated their effects on CO2 reactivity simultaneously. The current study examined the singular and interactive effects of the 5-HTTLPR genotype and neuroticism in predicting the affective and physiological response to a 35% CO2 challenge in a healthy sample of male and female students. From a large group of 771 students, 48 carriers of the low/low expressing allele (S/S, S/Lg, Lg/Lg) and 48 carriers of the high/high expressing allele (La/La) with the lowest and the highest neuroticism scores (77 females, 19 males; mean age ± SD: 20.6 ± 2 years) were selected and underwent a 35% CO2 inhalation. Visual analogue scales for anxiety and discomfort and the Panic Symptom List were used to assess affective symptomatology, while salivary samples and heart rate were assessed to establish the physiological response. A typical pattern of responses to CO2 was observed, characterised by increases in anxiogenic symptoms and physical panic symptomatology and a reduction in heart rate; however, no effect on salivary cortisol concentration was observed. Additionally, the CO2 reactivity did not differ between groups divided by the 5-HTTLPR genotype or neuroticism. Findings of the current study do not support a role for singular or interactive effects of the 5-HTTLPR genotype and trait neuroticism on affective and physiological reactivity to a 35% CO2 inhalation procedure.

Differential effect of the 5-HTT gene-linked polymorphic region on emotional eating during stress exposure following tryptophan challenge.

UNLABELLED: Stress and negative moods, which are thought to be partly mediated by reduced brain serotonin function, often increase emotional eating in dieting women (restrainers). Because the short (S) allele polymorphism in the serotonin transporter gene (5-HTTLPR) is associated with serotonin dysfunction, S allele compared to long (L) allele 5-HTTLPR genotypes may be more susceptible to stress-induced emotional eating. Consequently, serotonin challenge via tryptophan (TRP)-rich protein hydrolysate (TPH) may alleviate stress-induced emotional eating particularly in S/S allele carriers. We tested whether acute stress affects emotional eating in women with high or low dietary restraints depending on their 5-HTTLPR genotype and TPH intake. Nineteen female subjects who were homozygous for the short-allele 5-HTTLPR genotype (S'/S'=S/L(G), L(G)/L(G): restrainers vs. nonrestrainers) and 23 female subjects who were homozygous for the long-allele 5-HTTLPR genotype (L'/L'=L(A)/L(A): restrainers vs. nonrestrainers) were tested in a double-blind, placebo-controlled crossover study of stress-induced emotional eating following intake of TPH or a placebo. TPH intake significantly increased the plasma TRP/large neutral amino acid ratio (P<.0001) in the L'/L' group (70%) compared to the S'/S' group (30%). TPH reduced food intake in both groups, but in the L'/L' group, it also reduced stress-induced negative mood (P=.037) and the desire for sweet, high-fat foods (P=.011) regardless of dietary restraint. CONCLUSIONS: Since TPH caused a greater increase in the plasma TRP/large neutral amino acid ratio in the L'/L' group compared to S'/S' group, the exclusive beneficial effects of L'/L' genotype may be due to enhanced brain 5-HT function.

Affective and neuroendocrine stress reactivity to an academic examination: influence of the 5-HTTLPR genotype and trait neuroticism.

The current study examined the singular and interactive effects of the 5-HTTLPR genotype and trait neuroticism on affective and physiological stress responses to an academic examination in healthy undergraduate students. From 771 students, 46 short/short (S/S)-allele carriers and 48 long/long (L/L)-allele carriers with the lowest and the highest neuroticism scores (80 females, 14 males; mean age±SD: 20.3±1.7 years) were selected. Salivary cortisol concentrations, mood and perceived stress were assessed before and after a 2-h written examination and compared with a control day. Negative mood, perceived stress and cortisol significantly increased during the examination compared to the control day. Negative stress effects on mood and perceived stress were significantly larger for S/S-allele carriers compared to L/L-allele carriers, regardless of trait neuroticism. Since vulnerability to real-life stressors is an important risk factor for depression pathogenesis, this may be a mediating factor making S/S-allele carriers more susceptible for depression symptoms.

Effects of acute psychosocial stress exposure on endocrine and affective reactivity in college students differing in the 5-HTTLPR genotype and trait neuroticism.

Enhanced stress vulnerability has been implicated in the pathogenesis of affective disorders. Although both genetic (5-HTTLPR) and cognitive (neuroticism) factors are known to increase stress vulnerability, no experimental study has investigated the interaction between these two factors on psychobiological reactivity following acute stress exposure. This study used a balanced experimental design to examine the interaction between the 5-HTTLPR genotype and trait neuroticism in neuroendocrine and affective stress responses. From a large group of 771 students, 48 carriers of the short/short (S/S) allele and 48 carriers of the long/long (L/L) allele with the lowest and the highest neuroticism scores (77 females, 19 males; mean age ± SD: 20.6 ± 2 years) were selected and exposed to an acute psychosocial stressor. Mood was assessed before and after the stressor, and salivary cortisol concentrations were measured before and at 20, 30, and 60 min after stressor onset. Acute stress increased salivary cortisol concentration regardless of either 5-HTTLPR genotype or neuroticism, but it caused a less profound negative mood change in L/L compared to S/S-allele carriers with the lowest neuroticism scores. The 5-HTTLPR genotype influences affective reactivity to acute stress conditional upon neuroticism, improving resilience to acute stress in L/L-allele carriers if they do not already possess high cognitive-affective (neuroticism) vulnerability.

Effects of an acute alpha-lactalbumin manipulation on mood and food hedonics in high- and low-trait anxiety individuals.

Serotonergic hypofunction is associated with a depressive mood state, an increased drive to eat and preference for sweet (SW) foods. High-trait anxiety individuals are characterised by a functional shortage of serotonin during stress, which in turn increases their susceptibility to experience a negative mood and an increased drive for SW foods. The present study examined whether an acute dietary manipulation, intended to increase circulating serotonin levels, alleviated the detrimental effects of a stress-inducing task on subjective appetite and mood sensations, and preference for SW foods in high-trait anxiety individuals. Thirteen high- (eleven females and two males; anxiety scores 45.5 (sd 5.9); BMI 22.9 (sd 3.0)kg/m(2)) and twelve low- (ten females and two males; anxiety scores 30.4 (sd 4.8); BMI 23.4 (sd 2.5) kg/m(2)) trait anxiety individuals participated in a placebo-controlled, two-way crossover design. Participants were provided with 40 g alpha-lactalbumin (LAC; l-tryptophan (Trp):large neutral amino acids (LNAA) ratio of 7.6) and 40 g casein (placebo) (Trp:LNAA ratio of 4.0) in the form of a snack and lunch on two test days. On both the test days, participants completed a stress-inducing task 2 h after the lunch. Mood and appetite were assessed using visual analogue scales. Changes in food hedonics for different taste and nutrient combinations were assessed using a computer task. The results demonstrated that the LAC manipulation did not exert any immediate effects on mood or appetite. However, LAC did have an effect on food hedonics in individuals with high-trait anxiety after acute stress. These individuals expressed a lower liking (P = 0.012) and SW food preference (P = 0.014) after the stressful task when supplemented with LAC.