Theoretical models of the role of mothers' (Goodman, Reference Goodman2007) and fathers' depression (Ramchandani & Psychogiou, Reference Ramchandani and Psychogiou2009) in children's development have identified disturbances in parenting as an environmental pathway that explains the link between parents' depression and children's emotional and behavioural problems. However, the mechanisms underpinning impaired parent–child interactions in depressed parents have not yet been properly disentangled. This editorial sets out to identify possible mechanisms producing parenting difficulties. An improved understanding of these causal pathways will help to design interventions that have the potential to break the intergenerational transmission of psychopathology. The focus in this editorial is on affect, motivation, cognition and executive functioning (EF). Common genetic factors can also make an impact on both depression and parenting but a discussion of genetic mechanisms is beyond the scope of this editorial.

Before discussing existing studies and making further predictions based on their findings, we would like to emphasize two points. First, the hypothesized mechanisms may not be specific to depression but may also influence parenting in adults with other conditions including attention deficit hyperactivity disorder, anxiety and borderline personality disorder. Second, the mechanisms are inter-related and bi-directional influences are likely to occur. For example, negative affect can dampen motivation and readiness to implement parenting goals and weak cognitive control may hinder emotion regulation. Clearly, studies are needed to first establish associations between each of these processes and parenting and second, to investigate their possible interactions. An improved understanding of these processes will have implications for the development of more specific and potentially more effective treatments for parents with depression.

Affect can influence parenting and possibly lead to specific parenting behaviours (e.g. Dix, Reference Dix1991; Lovejoy et al. Reference Lovejoy, Graczyk, O'Hare and Neuman2000). Parents who score low on positive affect may interact less with their children or their interactions may have a ‘flat tone’ but probably they are not hostile or coercive, while parents scoring high on negative affect may be intrusive and excessively critical (Rueger et al. Reference Rueger, Katz, Risser and Lovejoy2011). Poor emotion regulation is also common in individuals who suffer depression. A study found that depressed mothers exhibit fewer and poorer emotion-regulation strategies compared with non-depressed mothers (Garber et al. Reference Garber, Braafladt, Zeman, Garber and Dodge1991). What are the implications of poor emotion regulation on parenting? This is an unanswered question but our prediction is that parents with an inability to regulate their emotions tend to be erratic and unpredictable. They may be emotionally unavailable and experience feelings of shame and guilt over their parenting role.

Researchers have also pointed to the importance of motivation in parenting and have shown that ‘maternal love engages a push–pull mechanism’ that deactivates brain areas implicated in social assessments and dealing with negative affect and that it ‘activates a specific pathway of the reward system of the brain’ (Bartels & Zeki, Reference Bartels and Zeki2004). Parenthood in the postpartum months is also associated with structural changes in brain areas that play a key role in a mother's motivation to be responsive to her infant (Kim et al. Reference Kim, Leckman, Mayes, Feldman, Wang and Swain2010). This study indicates that interactions with offspring may relate to increased grey matter in brain areas that facilitate a mother's motivation, but these changes in the brain may need adequate levels of mother–infant interactions in order to occur. Given that postpartum depression is highly prevalent in both parents, it is possible that in these cases depressed parents do not have optimal and frequent interactions with their newborns and so do not develop the brain changes or activation in reward-related areas noted in parents without depression (e.g. Kim et al. Reference Kim, Leckman, Mayes, Feldman, Wang and Swain2010). Thus both depressed mothers and fathers may not find the interactions with their children rewarding and may exhibit withdrawn and disengaged behaviours already noted in the maternal literature. With regard to activation in reward-related brain areas, Leuner et al. (Reference Leuner, Glasper and Gould2010, p. 465) indicated that ‘mothers and fathers might recruit similar neural circuitry, hormones and neuromodulators in the service of parenting behavior’, but whether new fathers show alterations in these functions when depressed remains to be determined.

Another process that may contribute to parental depression making an impact upon the quality of parent–child interactions is parental rumination (Stein et al. Reference Stein, Craske, Lehtonen, Harvey, Savage-McGlynn, Davies, Goodwin, Murray, Cortina-Borja and Counsell2012). Rumination, defined as ‘a mode of responding to distress that involves repetitively and passively focusing on symptoms of distress and on the possible causes and consequences of these symptoms' (Nolen-Hoeksema et al. Reference Nolen-Hoeksema, Wisco and Lyubomirsky2008, p. 400), is associated with negative thinking and deficits in problem-solving (Watkins et al. Reference Watkins, Baeyens and Read2009). In an experimental study mothers with either depression or generalized anxiety disorder and a group of psychologically healthy mothers were assigned to either a rumination/worry or a neutral prime condition. Interestingly, in comparison with the control group, rumination/worry had a significant negative effect on mothers' responsiveness to their babies' vocalizations for both depressed and anxious mothers although the effect was smaller in depressed mothers (Stein et al. Reference Stein, Craske, Lehtonen, Harvey, Savage-McGlynn, Davies, Goodwin, Murray, Cortina-Borja and Counsell2012). One interesting question is whether the strength of the rumination-impaired parenting link differs according to parent's gender. Women may ruminate more than men, but rumination in men can indicate a pervasive cognitive inflexibility (Davis & Nolen-Hoeksema, Reference Davis and Nolen-Hoeksema2000). We predict that it exerts a stronger effect on father–child rather than mother–child interactions. We also predict that in unstructured tasks there are differences in levels of responding between depressed and non-depressed parents, but in structured situations, such as helping the child with schoolwork, depressed parents do not differ from healthy parents because the demands of the task help them to be focused.

Finally, cognitive and EF deficits noted in adults with depression can be crucial in parenting (Bogels et al. Reference Bogels, Lehtonen and Restifo2010; Barrett & Fleming, Reference Barrett and Fleming2011; Johnston et al. Reference Johnston, Mash, Miller and Ninowski2012). Support for the role of cognitive and EF on parenting was provided by a study which found that harsh reactive parenting assessed during observed frustration tasks is common only in mothers with poorer working memory (Deater-Deckard et al. Reference Deater-Deckard, Sewell, Petrill and Thompson2010). Several hypotheses have been made about EF and parenting (e.g. Barrett & Fleming, Reference Barrett and Fleming2011; Johnston et al. Reference Johnston, Mash, Miller and Ninowski2012). One is that depressed parents do not have the cognitive flexibility to adapt to situations or their child's needs. Problems with prospective memory may affect a parent's ability to set developmentally appropriate goals for their children.

In future research, experimental work that manipulates, for example, the motivation of the parent (e.g. through exposure to rewarding stimuli) to examine the effects of the parent's motivation on parent–child interactions is needed. Longitudinal studies that focus on key developmental periods and investigate links between the mechanisms, parenting and children's functioning are also crucial. Such studies can uncover which mechanisms affect different parenting behaviours and put children into different developmental pathways. Valuable insight can also be gained by uncovering the factors that moderate (or mediate) these links. Contextual factors including marital conflict, single parenthood and low socio-economic status can exacerbate parenting problems. Children's difficult temperament or emotional and behavioural problems can affect parent–child interactions, through for example, increasing negative affect. Characteristics associated with the parent's condition (e.g. current versus past depression, co-morbidity, severity and chronicity) and the timing of exposure to parental depression (e.g. whether it occurs in a sensitive period of development) can moderate (or mediate) the link between depression and parenting. These factors can also differentially affect children's developmental outcomes. As a consequence, some groups of parents and children may be more vulnerable and in greater need of receiving treatment and others more resilient (Goodman, Reference Goodman2007).

There are direct implications for translation of the findings discussed above into clinical practice. One key question is where the best place to start is. Continued work aims to establish whether or not treatment of parental depression leads to better parenting and children's outcomes (e.g. Murray et al. Reference Murray, Cooper, Wilson and Romaniuk2003). Another option would be to target the aetiological mechanisms discussed. These mechanisms can affect children's development regardless of the parent being depressed at a particular time. For example, interventions can target parents' affect through behavioural activation or by training individuals who experience dysphoric affect to think in a more concrete and specific way (Watkins et al. Reference Watkins, Baeyens and Read2009). Further interventions can target poor EF via training that either enhances EF (Deater-Deckard et al. Reference Deater-Deckard, Sewell, Petrill and Thompson2010) or provides skills for compensating for these deficits that can lead to improved parenting (Bogels et al. Reference Bogels, Lehtonen and Restifo2010; Bailie et al. Reference Bailie, Kuyken and Sonnenberg2011). Interventions can also target a parent's emotion-regulation skills. A parenting intervention focused on parents' emotion socialization practices found that after the intervention parents displayed better emotion awareness and regulation and their children had decreased levels of behavioural problems (Havighurst et al. Reference Havighurst, Wilson, Harley, Prior and Kehoe2010).

To conclude, multiple mechanisms may explain the link between depression in adults and difficulties in their parenting role. Future research needs to empirically test these mechanisms and uncover their possible interactions. Such work can help us understand how parenting may put children of depressed parents at risk for psychopathology. An improved understanding of this area can also make prevention and intervention efforts more specific and effective and therefore help both depressed parents and their children.