The dangers of cannabis use compared to tobacco and alcohol - Part II

← Teil I: Verursachung von Krebs

The use of alcohol, tobacco and cannabis can have negative effects on the course of pregnancy and the development of the embryo and foetus with long-term effects on the health of the children, including reduced growth of the foetus, malformations and negative effects on mental development.

The best known and most serious is fetal alcohol syndrome, which is caused by alcohol consumption by pregnant women and is associated with malformations and serious effects on children's cognitive performance. It was first described in the Lancet journal in 1973 (Jones et al. 1973). Negative effects of tobacco use were already identified in the 1960s, effects of cannabis since the 1980s. A comprehensive review on the topic has been compiled by a working group of the American Society of Paediatricians (Behnke et al. 2013).

On the effects of cannabis use, there are two long-term studies in which children exposed to THC in the womb were followed for many years, with a large number of publications over a period of 20 and 30 years respectively, one study at the University of Ottawa (Canada) (Fried et al. 2003) and another at the University of Pittsburgh (USA) (Goldschmidt et al. 2012). The "children" in the Canadian study are now older than thirty years, those in the American study older than twenty years.

The frequency of drug use during pregnancy

in 2014, about 4.9 % (240 million people) of the world's adult population suffered from an alcohol use disorder (dependence, abuse), about 22.5 % (1 billion people) of all adults smoked tobacco products and 3.5 % (170 million people) used cannabis (Gowing et al. 2015). In the USA, a survey is conducted annually among 67,000 people older than 12 years. These data are then summarised for two years at a time. Table 1 summarises the results for the use of tobacco, alcohol and cannabis by women aged 15-44 years in relation to the presence of pregnancy in 2009-2010.

Mechanisms of action of drugs on the fetus

Drugs can harm the fetus in many ways. Early in pregnancy, during the embryonic period, i.e. in the first weeks, drugs can cause malformations. After the essential structural developments have been completed, drugs can exert even lesser effects, such as reduced growth or maturity, changes in neurotransmitters, i.e. signalling substances in the central nervous system, their receptors and the organisation of the brain. Drugs can also exert pharmacological effects on the mother, which can have indirect effects on the fetus.

Tobacco

It has been known for 50 years that cannabis use reduces the birth weight of newborns. In analogy to the fetal alcohol syndrome, the term "fetal tobacco syndrome" was proposed in 1985 in the journal of the American Medical Association (Nieburg et al. 1985). The more cigarettes are smoked, the lower the average weight of the newborn. However, children apparently make up this shortfall in the first two years of life. There is some evidence that tobacco consumption can lead to malformations, but this evidence is relatively weak, so this is not considered certain. However, there are clear indications of disturbances in muscle tone, behaviour, such as impaired orientation, as well as disturbances in the autonomic nervous system.

With regard to the long-term effects of tobacco consumption on the affected children, there are no clear indications of impairments of height and weight. However, some recent studies have shown increased overweight in these children. A number of studies have also found effects on behaviour, including increased impulsivity, hyperactivity and attention deficit disorders, which can be observed in early childhood and persist through adolescence and adulthood. These also manifest as criminal behaviour and increased drug use.

Studies of younger and older children exposed to tobacco during pregnancy have shown that, on average, they have a slightly lower intelligence quotient and impairments in learning ability and memory. Language development was also impaired, with poorer reading performance on average at age 9-12.

Definition of fetal tobacco syndrome

If an embryo (up to the ninth week of pregnancy) or fetus (from the ninth week of pregnancy) is exposed to nicotine and other toxins contained in tobacco smoke during its development, it will be impaired in its development and experience further developmental damage that can have a negative impact throughout later life. In extreme cases, this damage can even lead to premature birth or miscarriage. These damages, which can be diagnosed after birth, are summarised under the term Fetal Tobacco Syndrome.

Alcohol

Reduced growth in the womb is one of the important signs of fetal alcohol exposure, a symptom of fetal alcohol syndrome. Even moderate amounts of alcohol consumption during pregnancy are associated with a smaller average size of the newborn. Since the fetal alcohol syndrome was first described in 1973, many studies have appeared demonstrating malformations caused by alcohol during pregnancy. There are some clear abnormalities in the behaviour of the newborn, such as on the degree of alertness as well as changes in motor function.

With regard to long-term effects, there remains a negative effect on growth. The same applies to influences on behaviour from childhood into adulthood. These include attention disorders, school problems, social behaviour, criminal behaviour and drug use. Prenatal alcohol consumption is considered one of the most common preventable causes of intellectual impairment. The effects on the intelligence quotient can be highly variable. On average, affected children show poorer memory and lower abilities to perform complex tasks. The so-called executive function is impaired. Lower performance in mathematical tasks as well as in reading has been observed throughout the school years. Alcohol consumption is associated with impaired development and use of language, which is a possible reason for long-term problems in social interactions.

Definition of fetal alcohol syndrome

If an embryo (up to the 9th week of pregnancy) or foetus (from the 9th week of pregnancy) is exposed to alcohol and alcohol degradation products during its development, it is not only inhibited in its development, but also experiences further physical and cognitive developmental damage depending on the stage of maturity, amount of alcohol and individual disposition. These damages, which can be diagnosed after birth, are summarised under the terms fetal alcohol syndrome (in the case of the full picture) or fetal alcohol effects (in the case of symptomatically less severe manifestations). Fetal Alcohol Spectrum Disorder is used as a generic term.

Cannabis

Cannabis use generally had no effect on fetal growth in a number of studies. THC in pregnancy also does not cause malformations. However, in some studies subtle influences on behaviour as well as increased trembling. However, as this was not observed in all studies, such an influence is unclear.

With regard to long-term effects, THC exposure during pregnancy has no influence on the growth of children. Cannabis use also has no influence on the intelligence quotient. However, there is evidence that, on average, there are slight deficits in problem-solving tasks that require sustained attention, good visual memory, analytical understanding and integration of mental skills. In addition, THC is reported to have minor effects on learning and memory. There is no evidence of negative effects on language development, but there is evidence of possible reduced reading ability.

Conclusion

The most important results of this review are presented in Table 2, which is taken from the review of the American Society of Pediatricians mentioned above. According to this, there are by far the strongest drug effects on embryo and fetus from alcohol due to the possible development of a fetal alcohol syndrome. The effects of smoking tobacco or tobacco cigarettes are significantly lower. The effects of cannabis use are estimated to be the lowest. In children of women who have consumed cannabis during pregnancy, often no relevant effects are measurable in the first years of life because they are too small. Only in the course of school years such minor effects on behaviour and mental performance can be measured. Therefore, as with other medicines, medical use of cannabis products during pregnancy must be carefully considered. In the case of severe illnesses, cannabis probably represents a comparatively little harmful substance. Recreational use of cannabis during pregnancy should be avoided like the use of other substances (legal and illegal drugs, medicines).

Literature:

• Behnke M, Smith VC; Committee on Substance Abuse; Committee on Fetus and Newborn. Prenatal substance abuse: short- and long-term effects on the exposed fetus. Pediatrics 2013;131(3):e1009-

• 24. Fried PA, Watkinson B, Gray R. Differential effects on cognitive functioning in 13- to 16-year-olds prenatally exposed to cigarettes and marihuana. Neurotoxicol Teratol 2003;25(4):427-36. 

• Goldschmidt L, Richardson GA, Willford JA, Severtson SG, Day NL. School achievement in 14-year-old youths prenatally exposed to marijuana. Neurotoxicol Teratol 2012;34(1):161-7. 

• Gowing LR, Ali RL, Allsop S, Marsden J, Turf EE, West R, Witton J. Global statistics on addictive behaviours: 2014 status report. Addiction 2015;110(6):904-19. 

• Jones KL, Smith DW, Ulleland CN, Streissguth P. Pattern of malformation in offspring of chronic alcoholic mothers. Lancet 1973;1(7815):1267-71.

• National Survey on Drug Use and Health, 2010. Verfügbar unter: http://www.samhsa.gov/data/sites/default/files/NSDUHNationalFindingsResults2010-web/2k10ResultsTables/NSDUHTables2010R/PDF/Sect6peTabs71to78.pdf

• Nieburg P, Marks JS, McLaren NM, Remington PL. The fetal tobacco syndrome. JAMA 1985;253(20):2998-9.