In 2012, renowned novelist Daphne Merkin wrote a powerful essay for the New York Times about being a mother with depression—as well as her concerns that she might pass her condition on to her daughter, Zoe.

She wrote:

“Although I know that depression is not something you can catch from another person, like chickenpox, I fear that my susceptibility will somehow “rub off” on my daughter—that she might pattern her responses to life’s inevitable difficulties after my own.”

She is not alone in those concerns. Those who have watched parents and close family members struggle with depression often wonder if it is a heritable disease and whether it may be something they will eventually have to deal with in their own lives. And many, like Merkin, who have struggled with major depressive disorder, worry they will pass the condition on to their children, especially as new neurobiological evidence into the disease’s underpinnings emerge. The link is strong enough that some with depression have decided to forego having children altogether. One such person is comedian Sarah Silverman, who has publicly stated that she will not have kids because depression runs so strongly in her family.

So how heritable is depression? It may seem like a simple question. But it is one that necessitates a complicated answer.

Anecdotal evidence suggests that depression does, indeed, run in the family. But so do environmental factors that have also been linked to the development of depression, according to Healthline. And while genetic studies into the etiology of depression have offered many interesting insights, there is no one “depression” gene. There isn’t a single marker that turns off or on and determines whether you get the disease.

Unfortunately, there is no simple answer to the question about how heritable depression is. But here is what we do know about heritability and this disorder: A large-scale twin study conducted in Sweden looked at over 40,000 sets of twins. The twin part is important. You see, identical twins share the exact same genetic material. Fraternal twins do not. The scientists in this study compared the two different types of twins to look at potential genetic factors of the individuals who went on to be diagnosed with depression. Based on this large sample, and the ability to compare these different types of twins, they concluded that one’s genetic, or heritable, risk factor for depression was about 42 percent for women and 29 percent for men. The researchers called the result “moderately heritable.” But for those who are concerned about passing the disease down the family tree, a number like 42 percent may seem more significant than moderate.

Clinicians understand that depression is a complex disorder—one that can strike any person, anywhere, and at any time. Both biological and environmental factors are at play, and neither should be discounted. But the good news is that, regardless of how depression may arise, there are a variety of successful treatments available.

If you are feeling depressed, speak to your doctor. Help is available. And if your family has a history of depression, make sure your clinician knows that, too. This information can help a mental health professional make sure you get the care you need, when you need it—and get back to a healthy, stable mood.