An essential component of the human diet, L-tryptophan is critical in a number of metabolic functions and has been widely used in numerous research and clinical trials. This review provides a brief overview of the role of L-tryptophan in protein synthesis and a number of other metabolic functions. With emphasis on L-tryptophan’s role in synthesis of brain serotonin, details are provided on the research uses of L-tryptophan, particularly L-tryptophan depletion, and on clinical trials that have been conducted using L-tryptophan supplementation. The ability to change the rates of serotonin synthesis in the brain by manipulating concentrations of serum tryptophan is the foundation of much research. As the sole precursor of serotonin, experimental research has shown that L-tryptophan’s role in brain serotonin synthesis is an important factor involved in mood, behavior, and cognition. Furthermore, clinical trials have provided some initial evidence of L-tryptophan’s efficacy for treatment of psychiatric disorders, particularly when used in combination with other therapeutic agents.

Background Previous studies have found individuals with family histories of alcohol use disorders are more impulsive on some but not all laboratory behavioral measures, suggesting deficits on specific forms of impulse control. However, drawing conclusions is tenuous because these different measures have not been administered together in the same group of participants. Methods In the present study, we compared healthy 21–35 year old adults with family histories of alcohol related problems (FHAP+) or without such histories (FHAP−) on behavioral measures of response inhibition, response initiation, and consequence sensitivity impulsivity. FHAP+ (n=36) and FHAP− (n=36) participants were compared on performance on the Immediate Memory Task (IMT, response initiation), GoStop Impulsivity Paradigm (GoStop, response inhibition), Two Choice Impulsivity Paradigm (TCIP, consequence sensitivity) and Single Key Impulsivity Paradigm (SKIP, consequence sensitivity). Results FHAP+ individuals were more impulsive on the IMT and GoStop but not on the TCIP or SKIP. Conclusions These results suggest that response initiation and response inhibition impulsivity are increased in individuals with family histories of alcohol related problems despite not having alcohol or drug use disorders themselves. In contrast, increased consequence sensitivity impulsivity may be associated with additional risk factors such as more severe family histories of alcohol use disorders, or it may be increased as a consequence of heavy drug or alcohol use.

Impulsivity has been conceptualized as influencing the expression of suicidal behavior. Adolescence is a developmental period characterized both by a relatively high rate of suicide attempts and a high level of impulsivity. The current study examined two behavioral measures (delay reward and disinhibition) and one self-report measure of impulsivity among girls with suicide attempt histories. Girls with multiple suicide attempts performed more impulsively on measures of delayed reward, and had higher self-ratings of depression and aggression than girls with either one or no suicide attempts. The multiple attempter girl's preference for immediate gratification may directly increase vulnerability to suicidal acts in the context of distressing states or indirectly increase risk by creating poor life experiences over time. Keywords suicide attempts; impulsivity; adolescence; girlsAdolescence is a developmental period characterized by an exceptionally high rate of nonlethal suicide attempts that are associated with psychosocial problems extending into adulthood. While suicide is the third leading cause of death among teens, suicide attempts occur at much higher rates than deaths, especially for adolescents (McIntosh, 2009). For instance, while the rates of suicide death are similar among both adolescents and the elderly, adolescents are 50 times more likely to attempt suicide (McIntosh, 2009). This translates to about 1.5 million suicide attempts annually among adolescents in the United States (CDC, 207, 2009). Not only are suicide attempts common during adolescence, those who attempt suicide are at much greater risk of experiencing ongoing difficulties extending into adulthood, including further psychopathology, ongoing relationship problems, and death by later suicide attempts (Brent, Beugher, Bridge, Chen, & Chiappetta, 1999; Groholt & Ekeberg, 2009;King et al., 2001;Wong et al., 2008). Because of the relatively high incidence of suicide attempts occurring during adolescence and the long-term consequence of this behavior, there is a great deal of research interest in better understanding characteristics surrounding suicide attempts occurring in the adolescent period.Not only is adolescence characterized by a relatively high rate of suicide attempts, it is also a period of increased participation in impulsive behaviors. A host of neuro-biological and social changes occur during adolescence, increasing impulsivity and dysregulation of (Kelly Schochet, & Landry, 2004;Steinberg, 2008). While increased impulsivity is normative during adolescent development, there are a variety of sources of evidence suggesting that impulsivity is associated with suicidal behaviors, which may account for the relatively high rate of suicide attempts among adolescence. For instance, impulsivity is significantly higher among adolescent community-based and clinical samples with suicide attempts (Gorlyn, 2005;Horesh, 2001;Sanislow Grilo, Fehon, Axelrod, & McGlashan, 2003), increased impulsivity has been shown to be a predictor of ...

Adolescent suicidal behaviors and substance use are disturbingly common. Research suggests overlap of some of the etiological mechanisms for both adolescent suicidal behavior and substance use, yet clear understanding of the complex relations between these behaviors and their causal underpinnings is lacking. A growing body of evidence and a diathesis model (Mann et al. 1999;Mann, 2003) highlight the importance of impulse control as a proximal risk factor for adolescent suicidal and substance use behaviors. This literature review extends current theory on the relationships between adolescent suicidal behavior and substance use by: (1) examining how, when, and to what extent adolescent development is affected by poor impulse control, stressful life events, substance use behavior, and biological factors; (2) presenting proposed causal mechanisms by which these risk factors interact to increase risk for suicidal behaviors and substance use; and (3) proposing specifi c new hypotheses to extend the diathesis model to adolescents at risk for suicide and substance use. More specifi cally, new hypotheses are presented that predict bidirectional relationships between stressful life events and genetic markers of 5-HT dysregulation; substance use behavior and impulsivity; and substance use behavior and suicide attempts. The importance of distinguishing between different developmental trajectories of suicidal and substance use behaviors, and the effects of specifi c risk and protective mechanisms are discussed. Use of new statistical approaches that provide for the comparison of latent growth curves and latent class models is recommended to identify differences in developmental trajectories of suicidal behavior and substance use. Knowledge gained from these prospective longitudinal methods should lead to greater understanding on the timing, duration, and extent to which specifi c risk and protective factors infl uence the outcomes of suicidal behavior and substance use. In turn, fi ndings from these studies should inform researchers who conduct future treatment and prevention studies.Keywords: adolescence, development, suicide, substance abuse, behavior, risk and protective factors Epidemiological Findings of Adolescent Suicidal Behavior and Substance UseAdolescent suicidal behaviors are widespread and produce a signifi cant burden on healthcare systems. In the United States, suicide is the 4th most common cause of death among 10-14 year olds, and the 3rd most common cause of death among 15-24 year olds (Anderson and Smith, 2003). Suicide attempts are the primary reason for referral to child and adolescent psychiatric emergency services (Peterson et al. 1996). The incidence rates of suicide attempts among older adolescents range from 7% to 9% (CDC, 2004). Prospective fi ndings show that: (1) adolescents who attempt suicide are at risk of future non-lethal suicide attempts, and the risk increases with multiple suicide attempts (Goldston et al. 1999;Wingate et al. 2004); (2) adolescents who die by suicide have histo...