Is schizophrenia inherited from the mother or the father?

From either, at about the same rate. What matters is how closely you are related to the person who has it, not which side of the family they are on.

Does schizophrenia skip a generation?

It does not follow a fixed pattern, so it can look that way. The risk is spread across hundreds of genes, and a parent can pass on part of it without ever becoming ill themselves. That is how it appears in a grandparent and a grandchild with healthy parents in between.

Can a genetic test tell me whether I will develop schizophrenia?

No. Polygenic risk scores describe groups of people, not individuals, and are not used to predict it in one person. The exception is a chromosome test (microarray) for 22q11.2 deletion, which is worth doing if someone also has features such as a heart defect from birth, a cleft palate or learning difficulties.

My uncle has schizophrenia. Should I worry about my children?

Very little. An affected uncle puts your own lifetime chance at about 2%, and your children's close to the 1% everyone has.

I am 40 and my mother has schizophrenia. Am I still at risk?

Much less than the one-in-ten figure suggests. Most people who develop schizophrenia are diagnosed in their 20s, so by 40 most of the risk has already passed. Later first episodes do happen, and are somewhat more common in women.

Is bipolar disorder hereditary?

Yes, strongly. In the Danish national registers, children with one parent admitted to hospital for bipolar disorder had a 4.4% chance of bipolar disorder by age 52, and those with two such parents about 25%, against about 0.5% when neither parent had been admitted.

Is Schizophrenia Hereditary? Your Risk If a Parent or Sibling Has It

The numbers, by who in the family has it

Your relative with schizophrenia	Approximate lifetime chance for you
Nobody — the general population	about 1%
A first cousin, uncle or aunt	about 2%
A grandparent, or a half-brother or half-sister	about 3–6%
One parent	about 7–13%
A brother or sister	about 9–10%
A non-identical twin	about 7–17%
An identical twin	about 33–48%
Both parents	about 27–46%

The ranges bring together the classic family studies collected by the psychiatric geneticist Irving Gottesman and the later national registers of Denmark and Sweden. The registers tend to give the lower figures, because they count only hospital diagnoses up to a certain age.

The identical-twin row is the one to read carefully. Identical twins share all of their genes, and yet in more than half of pairs only one twin develops schizophrenia. Genes load the dice; they do not throw them.

Why your own number is probably lower — or higher

The table describes a person of unknown age with one affected relative. Your figure moves with four things:

Your age. Most people who develop schizophrenia are first diagnosed between their late teens and mid-30s; men usually earlier than women, and women have a second, smaller rise in their 40s and 50s. If you are 40 and have never had psychotic symptoms, most of your lifetime risk is already behind you.
How many relatives, and how close. Two affected relatives count for more than one, and a parent or sibling counts far more than a cousin. Relatives who reached their late 30s well count too, in the other direction.
What your relative’s diagnosis actually was. Schizophrenia, bipolar disorder with psychosis, severe depression and drug-induced psychosis are different conditions, although they share some of their genes. A parent with bipolar disorder raises the risk of schizophrenia as well, just by less.
Heavy cannabis use, particularly high-potency cannabis started in the teens, is one of the few risk factors a person can do something about.

Having children when schizophrenia is in the family

This is the question most people are really asking. The honest answers, by situation:

You have schizophrenia yourself. Each child’s chance is about 1 in 10. If their other parent has it too, roughly 1 in 4 to 1 in 2.
Your partner’s parent has it. Your child would be a grandchild of an affected person: roughly 3–5%.
Your partner’s aunt, uncle or cousin has it. Your child’s risk is barely above the 1% everyone has.
Your partner is past their mid-30s and has never been unwell. Their own risk has largely passed, which also lowers what they could pass on.

In every one of these, most children never develop schizophrenia.

What helps most is not a test but awareness. Treating psychosis early works better than treating it late, so it matters that the adults around a young person from an affected family know the early signs: pulling away from friends, a sudden drop at school or work, growing suspiciousness, or hearing and seeing things that others do not.

When a single genetic change is involved

In a small minority of people, schizophrenia is linked to one identifiable genetic change. The best known is 22q11.2 deletion syndrome, a small missing piece of chromosome 22 found in about 1 in 4,000 people. Roughly 1 in 4 people with it develop schizophrenia.

The clues are usually present long before any psychosis: a heart defect at birth, a cleft palate or nasal-sounding speech, low calcium, frequent infections, or learning difficulties. A chromosome test called a microarray can find it.

Most of these deletions are new in the child rather than inherited, but a person who has the deletion has a 50% chance of passing it to each child — a very different number from anything in the table above.