Although there have been some psychologists who studied the effect that separation has on development and found that this is true, there have also been several who have found that there are sometimes other factors that inhibit development, not just separation. Firstly, there was study carried out in 1992 by Bifulco et al which looked at 249 women, some of which had lost their mothers through separation or death before the age of 17.They found that these women were twice as likely to suffer from depression of anxiety disorder in later life. Therefore, this supports the statement as it is proving that early disruption does have an affect on development and being able to be sociable and form peers later in life.
Barrett did a study in 1977 which simply reviewed various other studies that had previously been completed. He found that if children have already formed a secure attachment then they can cope with early separation better than those who have an insecure attachment and they come especially distressed. This could be seen as supporting the statement however he hasn’t taken into consideration other factors that could be contributing to later distress. Rutler did two studies, in 1976 and 1981. Both of which can be seen as proving that disruption is harmful as he found that separation led to delinquency, however it can also be seen as criticising the statement because there could have been other issues that had a detrimental effect, for example poor living conditions or poverty.
Robertson did several studies on separation in children and one of his most interesting findings was that it wasn’t disruption that was harmful, but deprivation. One of the children he analysed John, was separated from his primary caregiver, his mother, however he was also deprived from any emotional care whatsoever and he found that this had more of an affect than the children who were able to seek comfort in others, i.e. nurses. Therefore, studies like these do not support the statement as it isn’t distinguishing the difference between separation and deprivation. Another study which doesn’t support the statement is Spitz and Wolf, 1946. This criticises it as it was proved that in some cases, children that were badly affected by separation when they were younger were able to recover and form perfectly good bonds with peers etc in later life.
So, although there is some evidence to prove that disruption of attachment is harmful to children’s development, there is also sufficient evidence to disprove it. Therefore you cannot say that disruption does affect later life however you cannot say that it doesn’t either. However, the evidence that we do have, (Bowlby’s maternal deprivation hypothesis, Bifulco et al,) is strong evidence and is widely known so it is a strong argument and therefore a valid point to say that is an infant is separated from their mother or father in early life then it will have some effect in one way or another to their later life.