Postpartum depression has been a recognized condition for years. In fact, the Greek physician Hippocrates recognized the symptoms as early as the 5th century B.C. However, many of the long-accepted truths about this illness are being questioned by new research. In addition, the latest studies are revealing that maternal mental illness can take forms other than depression. For a long time, it was believed that postpartum depression always appeared within the first few weeks after a mother gave birth. However, recent studies are now showing that the window for this illness is much wider. Research has revealed that depression can appear at various points during pregnancy, and that it can also appear as long as one year after giving birth. Research has also greatly expanded the scope of maternal mental illness. The latest studies show that women may experience symptoms of anxiety, bipolar disorder and obsessive-compulsive disorder in addition to depression. In all, studies have estimated that between one in five and one in eight women experiences symptoms of maternal mental illness. Depression remains the most common form of maternal mental illness, and an analysis of around 30 studies found that approximately 20 percent of women experienced some depression in the first year after delivery. In about half of these women the symptoms were significant enough to be considered severe. Approximately 11 percent of postpartum women begin to show obsessive-compulsive symptoms, and about half of them go on to develop obsessive-compulsive disorder. Women with depression frequently had symptoms of additional mental illness\u2014about two-thirds also experienced anxiety, while one-quarter exhibited symptoms of bipolar disorder. Symptoms Are Often Difficult to Predict One of the many challenges of maternal mental illness is that it remains very difficult to anticipate who will be affected. While a personal or family history of mental illness does appear to increase the odds of experiencing maternal mental illness, many cases appear without warning, in women with no history of prior mental illness. This can result in delayed diagnosis and treatment, which can sometimes put both mother and child at risk. Several U.S. states now have laws in place to encourage women to be screened for maternal mental illness. In addition, a provision in the Affordable Care Act will increase efforts to diagnose and treat maternal mental illness, and also step up research in this field. Depression that begins during pregnancy can be particularly difficult to recognize. Many women in the last trimester of their pregnancy are frequently tired and irritable\u2014two of the most recognizable symptoms of depression. When pre-partum depression continues after delivery, it may remain hard to detect because there is not a noticeable change in mental attitude from pregnancy. The causes of maternal mental illness are roughly understood and usually include a combination of hormones, genetics and external stressors. However, the exact combination that results in symptoms of mental illness is still largely a mystery, which is what makes the appearance of maternal mental illness so difficult to predict. In many ways, it is not surprising that the huge spike in hormones during pregnancy and corresponding drop after birth can cause emotional disruption. But why many women experience no symptoms or mild symptoms of mental illness while others become seriously ill remains unknown. Consequences of Maternal Mental Illness In rare cases, serious maternal mental illness can have tragic consequences and result in the death of mother or child or both. But while intrusive thoughts of harming their children are commonly reported among women with maternal mental illness, very few act on them. Nevertheless, research increasingly suggests that the consequences of maternal mental illness can go beyond the risk of violent behavior. If the illness goes untreated, it can be difficult for women to bond with their babies or to care for the children properly. If the symptoms are disruptive enough, there can be long-term consequences for the child\u2019s cognitive development.