Genetics and personalized medicine

On the other extreme of the health strategy continuum, the most escalated level of personalized medicine is linked to the human genome mapping that is expected to result in a substantially enhanced ability to assess health risk and damage of individuals based on their exposure to risk agents and their differential susceptibility and resilience to such agents (Kumar et al., 2015). However, human genome sequencing still faces some relevant scientific challenges for real-world medical applications such as those related to the number of DNA sequence variants and the delineation of the novel molecular pathways involved in the pathogenesis of the phenotype (Marian, 2012). Also, a number of moral and ethical issues have been raised from a variety of scientific, medical, and social sectors, regarding, for example, data sharing and protection of DNA databases, the potential genetic manipulation for non-medical reasons, the regulation on the acquisition and use of genetic information, mandatory genetic screening, and genotype-based discrimination in health insurance (Carroll and Ciaffa, 2003). Another issue is that the identified causal mechanisms or pathways are not homogeneous across individuals, and their average profile may not be actually representative for any individual; also, in the case of non-infectious diseases, most risk factors are associated with rather low positive predictive values (Rockhill, 2005).

The challenges faced by the P4-predictive, preventive, personalized, and participatory-medicine seem to be both economic and related to the integration of the population approach into science, practice, and health policies addressing the four components. The current practice of medicine is already conducted in a personalized manner, in most cases for the differential gender, age, and race characteristics, and some other clinical factors, and practice is also expected to be evidence based, yet P4 medicine could provide and implement novel personalized diagnostic and therapeutic applications. Although a large variety of challenges of scientific nature related, for example, to the understanding of underlying biological pathways and molecular networks, and the identification of biomarkers still remain, the operational and the economic aspects of the implementation of personalized medicine seem to be equally challenging. Major issues include addressing the balance between the patient’s clinical merit for and benefit from biomarker-based diagnostics and treatment and the assessment of the aggregate population cost; establishing healthcare standards; and data security and mining. The participatory component of personalization requires understanding and integrating the social and behavioural elements involved in individual decision making already during the development of a new application.

Regarding the potential to integrate genetic variations into the prevention strategies for addictive substance use and behaviours, one issue is that genes that potentially modulate the variation in the risk for addictive substance use are not substance- specific (Li & Burmeister, 2009). Relevant evidence indicates that many genetic factors influencing addiction to different substances are shared, and these shared genetic pathways seem to be also involved in other psychological constructs such as impulsiv- ity and compulsivity (Koob & Volkow, 2010). Genetic influences significantly overlap across alcohol, nicotine, and illegal drugs, and also across addictive substance use and other externalizing behaviour conditions (Agrawal et al., 2012). As for illegal substances, significant proportions of genetic influence on addiction to a variety of these substances could be attributed to a common genetic vulnerability (Kendler et al., 2003). In addition, comorbidity across addictions and also between addictions and other mental illnesses is partially owing to genetic factors (see Box 5.5).

Box 5.5 Genetic research is essential for high-risk approaches

Despite the current difficulties to integrate findings on genetic susceptibility to addictive substances and behaviours into an optimised delivery of effective preventive interventions in public health, genetic research is essential to improve treatment approaches for the group of high-risk individuals whose substance use and behaviour problems persist despite the environmental and structural changes, and even specialized treatment.

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