Depression in either parent is associated with an increased risk of child psychopathology and other developmental difficulties, with the risks continuing into adulthood.⁽³⁾ The longest running longitudinal study⁽⁴⁾ found that, as well as a three-fold increase in major depressive disorder, the adult offspring of depressed parents had increased rates of anxiety disorders and substance dependence, as well as greater social impairment and physical health impairment. There has been a large body of research focusing on depression affecting mothers in the postnatal period, with studies demonstrating that infants and children have an increased risk of emotional and behavioural problems.⁽⁵⁾ Some studies have suggested that children’s cognitive development may also be affected, although the results from studies are not consistent.⁽⁶⁾ Similarly, there is a suggestion that boys may be more affected than girls in early childhood. As the children enter adolescence an increased risk of mood and anxiety disorders emerges.⁽⁷⁾ More recently research in developing countries has shown an association between postnatal depression and an increased risk of physical health problems in infants such as poor growth and diarrhoel illness.⁽⁸⁾

Much less work has been done on depressed fathers, although consistent evidence is now beginning to emerge of an independent effect of paternal depression on children’s development.⁽⁹⁾ The overall impact may be less than that of maternal depression, and there are also conjoint effects to consider, as depression in one parent can often co-occur with depression or another psychiatric disorder in the other parent. Similarly there may be protective effects if one parent remains well.⁽¹⁰⁾

While genetic factors clearly play an important role in the transmission of risk from parents to children, environmental factors, and the interactions that occur between genetic and environmental factors, also have substantial influence.^(11,12) In the case of depression, the core symptoms of low mood, loss of interest and low energy can have a significant impact on parenting capacity and parent-child relations. These include a parent’s capacity to be responsive, consistent, and warm when interacting with their children, particularly in the first few years of life. For example, depressed mothers may be less vocal, less positive, and less spontaneous than controls, more negative, unsupportive, and intrusive, and have more difficulty in communicating and listening to their young children.^{(13, 14)}

Depression in either parent is strongly associated with marital discord.⁽¹⁵⁾ This may play a key role in mediating the effects of parental depression and may be a more proximal predictor of child outcomes than depression.⁽¹³⁾ The way in which conflicts are resolved may be very important and depressed parents are likely to use less effortful strategies, such as withdrawal. Children are generally more at risk as they are exposed to an increased number of risk factors, and children whose parents are depressed are particularly at risk if they are also socio-economically disadvantaged.

The direction of effects is not all from parent to child, and temperamental and behavioural factors in the child may also contribute to increasing family discord, parental psychiatric disturbance, and parenting impairments, and ultimately to disturbances in parent-child attachment. Infant irritability and poor motor control, measured before the onset of any maternal depression at 10 days postpartum, increase the risk that a mother will become depressed.⁽¹⁶⁾ The influence of parental depression on child development thus represents a complex bidirectional interaction between individual vulnerability (which may be genetic), influences of depression on parenting characteristics, parent–child relationships, the wider context of the parental relationship, and other aspects of social disadvantage.

Parents with a diagnosis of schizophrenia have a greatly increased risk of having children who later develop schizophrenia themselves. Risks to child development are identified from birth, with an increased likelihood of obstetric complications, not fully accounted for by maternal behaviour during pregnancy, or by genetic risk.⁽¹⁷⁾ During childhood, prior to the onset of any psychiatric symptoms, attentional problems similar to those found in adult schizophrenic patients have been identified and these problems not only persist into adulthood, but attentional problems have been identified as key neurobiological indicators of risk for subsequent schizophrenia or other psychopathology in adolescence and young adulthood.⁽¹⁸⁾

Social difficulties with peers and teachers are found in many longitudinal studies of children with schizophrenic parents,⁽¹⁹⁾ although not necessarily to a greater extent than in children with parents suffering from affective disorder and a higher IQ can be protective. Social relationship problems and associated thought disorder may become more marked in adolescence and seem to be predicted by attentional problems.⁽¹⁸⁾ As young adults, children of schizophrenic parents are at high risk for schizotypal behaviour, although this broader range of difficulties does not necessarily distinguish them from parents with affective illness.

A pattern of disturbed communication has been described in families with a schizophrenic parent,⁽²⁰⁾ but the importance of these interactions in explaining long-term outcomes has been questioned.

Overall, cognitive and attention difficulties appear to be largely associated with specific brain abnormalities linked with schizophrenia, but other kinds of childhood problems are probably influenced
more by the general family disruption associated with a parent who requires hospital admission and who may have difficulties with employment and other social relationships beyond the family.

Eating disorders occur commonly among women of child-bearing age.⁽²¹⁾ Studies have raised concern that mothers’ attitudes and behaviours regarding food and body shape, may influence their children’s feeding, and ultimately the children’s own attitudes to body shape and eating.⁽²²⁾ Children are particularly vulnerable at two stages of development—infancy and adolescence. During infancy feeding and mealtimes take up a significant part of the day and provide important times for close communication between parents and children. A Scandinavian study has indicated that failure to thrive may be a risk in the first year amongst women with a history of anorexia nervosa.⁽²³⁾ One controlled observational study of 1-year-old children of mothers with eating disorders found that the mothers were intrusive with their infants during both mealtimes and play, and they expressed more negative emotion and conflict during mealtimes than controls, and allowed their children less autonomy.⁽²⁴⁾ Furthermore, infant weight was independently and inversely related to mealtime conflict.⁽²⁵⁾ Follow up studies of children of mothers who have experienced eating disorders in the postnatal period indicate that in middle childhood they are more likely than control children to value themselves by body shape and weight, and to use dietary restriction.^{(22, 26)}

During adolescence children become more aware of societal pressures and develop increasing interest in body shape and attractiveness while preoccupied with their own concerns about food, body shape, and weight. Children may model themselves on their parents, and parents may influence their adolescent children directly by expressing attitudes towards their children’s weight, shape, and eating habits. However, it should be emphasized that, in common with most parent psychopathology, the children of parents with eating disorders are not invariably adversely affected. Some parents manage well and their children develop without apparent problems.

A substantial body of evidence has been amassed on the effects of parental alcoholism and substance abuse.⁽²⁷⁾ They are wide ranging, identifiable throughout development, and work has highlighted the importance of the social effects on the child in addition to physical and psychological outcomes.⁽²⁸⁾ Both genetic and environmental factors seem to be involved.

The impact of maternal alcoholism on the developing child can be found from the prenatal period.⁽²⁹⁾ Present in 0.01 to 0.03 per cent of normal births, foetal alcohol syndrome appears in 5.9 per cent of births of alcoholic women. There is also considerable evidence that infants exposed prenatally to heroin and cocaine are at increased risk of a number of developmental difficulties which may persist throughout childhood.⁽³⁰⁾

Studies of outcome consistently describe impaired cognitive and social development in children of alcoholics and heroin users.^{(27, 30)} An increased risk of attention-deficit hyperactivity disorder, attention problems, and impulsivity in children of alcoholics is the most consistent finding. Children of drug abusers may also be more aggressive and have fewer friends and are at risk for criminality, depression, anxiety, and somatic problems. Children of alcoholics have an increased risk of becoming alcoholics themselves and, similarly, children of drug abusers also have an increased risk of drug abuse in adolescence, although many are resilient and do not develop similar problems themselves.

Social factors such as poverty and social isolation are known to influence child development adversely and it has been difficult to differentiate between the effects of the disorder and the associated adversity. Substance abuse in the parent may lead to impaired parenting and an impoverished social environment, leaving children vulnerable to neglect or abuse and contributing to impaired social and cognitive functioning, psychopathology, substance abuse, and delinquency but the relative impact of each factor has yet to be resolved. Studies have identified deficits in parenting behaviour and, in particular, neglect and harsh discipline.⁽³¹⁾ Divorce and marital conflict are also more likely and there is evidence of assortative mating, all of which are likely to compound the risk for the children.