Tuesday September 7 2010
Postnatal depression is only clinically defined for women
Depression hits one in five men after they become fathers, reported the Daily Mail. The newspaper quoted the authors of a study as saying that this depression is “caused by extra pressures that come from having children, such as loss of sleep and increased responsibilities”.
The story is based on research which looked at depression in both mothers and fathers, from the birth of their child until they were 12 years old. It found that 39% of mothers and 21% of fathers experienced a depressive episode, with the highest risk being in the first year after birth.
This very large study provides some useful information about the rates of depression and the factors that may make new parents more vulnerable. It seems reasonable to suggest that the stress of new fatherhood may put men at risk of depression, and the study raises the question of whether new fathers should be screened for depression, as new mothers are.
Depression is common, with about one in ten people thought to be affected at some point in their life. This study did not compare rates of depression in fathers with those in a similar group of men who did not have children so it is unclear from this study if fatherhood puts men at increased risk. In addition, it did not look at the severity of the depression.
Where did the story come from?
The study was carried out by researchers from the UK Medical Research Council (MRC) and University College London and was funded by the UK MRC. It was published in the peer-reviewed medical journal Archives of Pediatric and Adolescent Medicine.
The study was reported fairly in the media, although both the Telegraph and Guardian referred to postnatal depression in men, when it is only clinically defined for women. None of the papers pointed out that the study did not compare rates of depression between parents and people without children.
What kind of research was this?
This large prospective cohort study used a primary care database to look at rates of both maternal and paternal depression. It followed families from the birth of their child to when the child reached the age of 12 years. It also looked at factors that might increase the risk of depression in parents.
The authors point out that depression in parents is thought to adversely affect the behaviour and development of their children. Postnatal depression in women is a specific, recognised clinical disorder. It usually occurs in the first few months of motherhood and can be severe, making it difficult for a mother to bond properly with her baby.
Few studies of paternal depression exist, although there is evidence that it is not uncommon and that rates are higher than in the general adult male population. There is also little research into rates of depression through the early years of parenthood.
What did the research involve?
Researchers identified a total of 86,957 families (called “mother, father and child tryads”) using a national primary care database called The Health Improvement Network (THIN). They identified all births in the database from 1993 to 2007 and then, using additional information, linked each birth to the mother. They then linked these mother-baby “dyads” to a household where there was one single man registered, who could be the father. Families where the age difference between the mother and the man was more than 20 years were excluded, as were individuals under 15 years old.
The researchers recorded the age of the parents when the baby was born. They also looked at levels of social deprivation, using an accepted index, based on individual postcodes (one being the lowest deprivation and five the highest).
The researchers identified depressed parents by looking for a particular code in the medical diagnosis coding system used in general practice (Read), which indicated a diagnosis of depression, or by looking at prescriptions for antidepressants. In their code searches, the researchers excluded other conditions, such as bipolar disorders, depression with psychosis and low mood. They also excluded parents who had been prescribed antidepressants for anxiety and panic disorders without depression being present. They then identified separate episodes of depression for each individual, with each new episode having a gap of at least one year with no depression.
From this information, they calculated the rate of parental depression, from the birth of a child up to when the child was 12 years old (as far as the data were available). They used standard statistical methods to analyse associations between depression, parental age at the birth of the child and social deprivation, as well as parental history of depression before the birth.
What were the basic results?
The study found that the overall incidence of depression, from the birth of the child up to the age of 12, was 7.53 per 100 person years (the accumulated amount of time that the people in the study were being followed up) for mothers (95% confidence interval [CI] 7.44 to 7.63) and 2.69 per 100 person years for fathers (95% CI 2.64 to 2.75).
Depression was highest in the first year after birth with 13.93 and 3.56 per 100 person-years among mothers and fathers respectively. It decreased sharply when the child reached one year old. By the time the child had reached 12 years old, 39% of mothers and 21% of fathers had experienced an episode of depression.
A history of depression before parenthood, lower parental age at the birth of a child (15 to 24 years) and living in areas of higher social deprivation were all associated with higher incidence of parental depression.
How did the researchers interpret the results?
The authors say this is the first study to assess incidence of depression in both mothers and fathers throughout the course of their offspring’s childhood. They say there is a significant risk of either parent becoming depressed soon after the birth of a child (although the risk is higher in mothers) and that clinicians need to be aware of this. Younger parental age, social deprivation and a history of depression increase the risk. They suggest that policymakers should consider screening for fathers as well as mothers.
This large study, which followed nearly 87,000 families for several years, suggests that fathers are at risk of depression, especially in the first year of parenthood. However, the risk is lower than it is for new mothers, and we do not know how it compares to rates of depression among similar-aged adult males in general. The size of this study increases its statistical power and makes its findings about depression rates more reliable (although, as not everybody reports depression to their GP, rates may be underestimated). The study has some limitations:
- As the authors note, it is unclear whether the adult males identified were fathers of the children, despite the researchers’ efforts to minimise uncertainty.
- They also note that the definition of depression was based on diagnoses made by GPs, not on standard classifications.
- The researchers say they did not look at other factors which might be associated with depression, such as a partner’s depression, the couple’s relationship and stressful life events.
- The follow-up data on the families varied in length and tended to reduce with time, which could make the findings less reliable. For example, follow-up data at one year was available on 84% of fathers, but was only available on 5% of fathers at 12 years.
- It is also not possible to ascertain from this study how many children the families had in total, and whether previous or subsequent births affected depression rates.
- The study did not include single-parent households, either male or female. Researchers noted that nearly half the households identified did not include an adult male and these were excluded.
As the authors admit, further research is needed to confirm these findings and to look at other factors associated with depression, so that GPs can identify vulnerable patients.