Links Between Cigarettes, Alcohol & Marijuana

Attentional behavior can be examined in several ways. One of the most frequently used approaches employs a procedure called continuous performance task (CPT). In essence, CPT involves the presentation of sequential stimuli over a particular length of time. The subject is instructed to press a response button when a particular stimulus is presented and to withhold responding when nontarget stimuli occur. Among the measures derived from this technique are correct identification, errors of omission (misses), and errors of commission (false alarms). A further method used to examine aspects of impulsivity has been the technique Differential Reinforcement of Low Rate Responding (called DRL). In the DRL situation the subject is reinforced for a response that occurs after a certain set time has passed since the emission of a previous response. Furthermore, responses that occur prior to the elapsing of the specified time are not reinforced and result in the timer governing the requisite time interval being reset.

A somewhat less direct way of examining attentional behavior is to note performance on tasks which clearly have an attentional component, e.g., memory tests. A third approach to examining attentional behavior is through observational measures. They may take the form of the experimenter observing the activity of the child in the laboratory or by standardized questionnaires being filled out by individuals familiar with the child (parents or teachers).

Several studies have noted an association between maternal cigarette smoking during pregnancy and sustained attention deficits in the offspring. On one CPT test of 4-year old children of smokers, the children made significantly more errors of omission (not pressing the cue button), and commission (pressing the button at the wrong time) and had a lower ratio of correct to total responses (40). These results were statistically adjusted for maternal alcohol use and other background variables.

Several studies have reported results consistent with the observations of the 4-year-old children just cited. Aspects of attentional behavior in 4 to 7 year-olds using both a visual and an auditory CPT were found to be associated with maternal smoking (18). After controlling for potentially confounding variables including maternal alcohol and marijuana use and postnatal second-hand smoke, exposure to cigarette smoking during pregnancy was related to an increased activity level of the children (assessed by a sensor under the cushion of the child's chair) and increased errors of commission, particularly in the auditory task. Studies using samples derived from the National Collaborative Perinatal Project have noted increased hyperactivity, impulsivity, and shorter attention span in the 7-year-old offspring of smokers (25,26). In an early retrospective study, Denson et al. (7) matched 20 methylphenidate (ritalin) sensitive hyperactive 5 to 15 year-old children to two control groups. The mothers of the hyperactive children smoked considerably more than the mothers of the children in the reference group. However, in a study with relatively few heavy smokers and using naturalistic observations of 4 year-olds (19), no significant relationship between the mothers' smoking and childhood attention was found.

Several reports have examined attention in preschoolers and school-age children who had been exposed prenatally to alcohol. Patients with a diagnosis of Fetal Alcohol Syndrome (FAS), whose mothers typically were considered to be alcoholic, often have marked attentional deficits and impulsive behavior that are evident in early school environments and that persist into adolescence and adulthood.

Several studies have investigated attention and/or activity in children who did not show FAS but were exposed to alcohol prenatally. Using observational data, the 4-year-old offspring of women with moderate drinking in pregnancy were observed to have shorter attention spans and more frequent instances of inattention (19). Using a CPT task, performance of children at 4 and at 7 years of age on attention tasks and impulsivity was negatively related to maternal nonalcoholic levels of drinking (4,32,38).

Unlike the situation with cigarettes and alcohol, there is very little literature that has examined the association between sustained attention in young children and prenatal marijuana exposure. Even indirect evidence is very sparse. At 4 years of age, although general intellectual measures were not related to prenatal marijuana exposure, the children of regular users had lower memory scores that persisted after controlling for potentially confounding factors (13). It is possible that attentional factors may have contributed to this association. In a recently published preliminary report 6- to 9-year-old offspring born to maternal marijuana users, in comparison to children of nonusers, were rated by their mothers as being more distractible and were assessed as scoring more poorly on a visual memory tasks (27). However, these observations did not remain statistically significant after controlling for the age of the mother at the time of delivery and the home environment.

The following research examined aspects of attentional behavior in 6 year-old children exposed prenatally to marijuana, cigarettes, and alcohol. The subjects were participants in the Ottawa Pre-natal Prospective Study which is an ongoing longitudinal investigation assessing the effects of several drugs used socially during pregnancy in a low-risk, predominantly middle-class sample (15). The background information available from these women includes both a detailed history of drug use during pregnancy and extensive information with respect to demographic variables.

Children diagnosed with Attention Deficit Hyperactive Disorder (ADHD) and also diagnosed simultaneously with aggressive behavior were found to have low levels of the brain neurotransmitter called serotonin, when compared to ADHD children who did not show aggressive behaviors. This 1994 research conducted at the Mt. Sinai School of Medicine is one of the first studies to provide a biological explanation for their aggressive behavior. The subjects were twenty five 7-11 year old boys who were rated as "aggressive" by their teachers using the Conners Teacher Questionnaire. The child was defined as being aggressive if he demonstrated at least one of the following behavior traits consistently; physically cruel to animals, forced someone into sexual activity, used a weapon in more than one fight, initiates physical fights, stealing with confrontation of the victim, or is physically cruel to people.

The deficit in serotonin levels appears to be unique to Attention Deficit Hyperactive Disorder (ADHD) aggressive children since abnormal serotonin levels were not always found in other studies of adults with aggressive behavior.

Researchers reported in the 1990 International Journal of Neuroscience that zinc supplementation may improve behaviors in ADHD children.. Zinc deficiency was found to occur in a small subgroup of ADHD patients and, according to the researchers, suggests that the disorder may be associated with decreased melatonin secretion. Since melatonin stimulates serotonin synthesis (Aldegunde et al. 1985) and since serotonin deficiency has been linked to aggressive behavior (Muhlbauer, 1985), the researchers stated it is possible that the high number of conduct disorder and aggressive behavior in ADHD patients could be related to a reduction in melatonin and serotonin levels in the brain. It is believed that the diminished nutritional zinc intake may limit the ability of the pineal gland to synthesize melatonin.

Dr. E. L. Arnold suggests that zinc supplementation might enhance the therapeutic efficacy of amphetamines in a subgroup of patients with ADHD. Previous research has shown that various drugs including cocaine, L-dopa, and amphetamines increase melatonin production (Acta Physiol. Scandinavia, 87:113-120, Backstron and Wetterberg)

In conclusion Dr. R. Sandyk states,