GENETICS, GENETIC COUNSELLING, IN VITRO FERTILIZATION AND

PSYCHIATRY

BY

David M. Ndetei Professor of Psychiatry

Genetics, Genetic Counselling, In Vitro Fertilization And Psychiatry

PREAMBLE 1) There is a misconception that mental disorders are an

exception when it comes to genetic predisposition to illness, more than is the case with most metabolic and physical conditions. Nothing could be further from the truth – e.g. in the case of diabetes, hypertension, most metabolic diseases

2) Whether physical condition or a mental disorder condition, genes express themselves through chemicals/neurotransmitters

3) I do not intend to go to specific conditions but would like to highlight the principles involved.

SOME PRINCIPLES 1) Dominant Genes:

With complete penetrance

With incomplete penetrance

Anybody with a dominant gene for a given conditions has a 50% chance of developing the condition. But not all people with Dominant Genes for a particular condition develop the condition. And for those who develop the condition, it varies considerable in degree

2) Recessive Genes – You need to inherit such genes from both biological parents for the genes to find expression

3) Poly genetic i.e. Several genes acting synergistically to produce a condition

FAMILY STUDIES ON GENETIC CAUSES FOR SCHIZOPHRENIA

1) Identical Twins – Same biological parents, same sex, share same genes

2) No identical Twins – same biological parents, but share only ½ of the genes – Same or different sexes

WHY MOST OF THE STUDIES HAVE BEEN DONE IN DENMARK

Denmark has a standard practice going back to early last century on personal records – from birth across the lifespan. With a touch of a bottom you can generate the Genealogy of a person going back to many generations

STUDY DESIGN IN FAMILY STUDIES

Using twins born of a schizophrenic parent who were then adopted, to determine the % congruence (a, b, c, d – see table) of developing schizophrenia

Both adopted by one family -i.e. same environment

Each adopted by different family - i.e. Different environment

Identical a b Non-Identical c d

Note: Environment could be: - Physical, psychological, social, cultural, past events, economic/poverty, ignorance e.g. a obese man or obese woman is a sign of a caring spouse or Nyama choma with a lot of salt to make it testy and as often as possible is a sign of good eating or doing physical work on your garden is a sign of poverty

Results - % congruence of developing schizophrenic illness

1. a> b> c> d 2. a + b > c + d

Conclusion: The environment has a modulating effect on the expression of the biological consequence of genes. We call this Genetic Plasticity

CURRENT STUDIES ON GENETIC CAUSES FOR MENTAL ILLNESS

1)Genotypes – determined in a laboratory

2)Phenotypes - signs and symptoms

3)Genotypes compared with phenotypes to determine congruence

CLINICAL IMPLICATIONS 1) Having a genetic predisposition for a certain

condition does not mean the person will develop the condition e.g. a person with a genetic predisposition for diabetes can significantly reduce the clinical chances of developing diabetes if they are adopt healthy lifestyles.

2) Genetic plasticity means it is the combination of genes and the environment that determines phenotypes i.e. the disease expression

3) In genetic counselling for a specific condition, the counsellor needs to do the following: -

a) When is genetic counselling sort - Usually for couples who are planning pregnancy i.e. whether to allow the pregnancy to occur or in a couple where she is pregnant and they want to know whether to allow the pregnancy to continue

b) What do you do? Check the genetic dominance, recessiveness and

polygenetic predisposition

You can only talk about probabilities and not absolutes

Take history if the condition had occurred in the children or close relatives of the person seeking for genetic counselling

The final decision is solely the responsibility of the person seeking the counselling

The same principles will apply if the subject under consideration is in Vitro-fertilization. The Risk is if they do not know the donor.