I’ve been thinking a lot about depression lately. Not because I myself have been depressed – I, luckily, have been free of the black dogs for about ten years now, and I don’t think they’ll come back. No, I’ve been thinking a lot about depression because I’ve had to stand by and watch, helplessly, as many of my friends and family have fallen into its clutches.

Depression: it’s such a funny thing. You watch people who are intelligent, young, attractive and healthy – who seem to possess all the ingredients for happiness – fall into the most tragic despair. Meanwhile other friends, who grew up abused and poor, embrace life every day with a smile on their face.

You want to scream: Stop moping, for the love of God. Go and plant a garden, or volunteer or something. Sitting around feeling sorry for yourself isn’t helping anyone. Life is short, kiddo – we could all be dead tomorrow. Don’t you see that you’re just wasting time?

But then you restrain yourself. Shouting isn’t going to help. And, logically, you know that they can’t help the way they feel.

Now, there has been an excessive tendency in the past few decades to see depression purely as the result of biochemical pathways thrown out of balance – an internal condition to be solved internally with pills and potions. It is most certainly true that purely physical events can result in depression. Impaired thyroid function can lead to post-partum depression. Wacky hormones in adolescents can sure as hell make you lose the will to live. Any junkie (or any kid who raved on E every weekend for a year) can attest that too many chemicals left their brain unable to regulate itself properly.

But, there are of course a million things that can happen in our lives that can make us depressed: failure, divorce, illness, death. On and on.

Depression is, as they say, a multifactorial disease: there is rarely one definitive cause. It is usually the result of a combination of things – such as losing your job, the death of a friend, and a genetic predisposition – all conspiring to push you down into a black pit of despair.

Teasing apart all the different factors that can predispose you to depression, and how those factors combine and interact, is, to say the least, a dizzying affair. Every week studies emerge that examine the influence of one factor or another.

This study however, I find particularly interesting.

Researchers followed more than 200 men for three decades, starting at about age 18, interviewing them periodically. For statistical reasons (that are far too boring for me to bother elaborating on), a study like this, that follows the subjects prospectively over time (as opposed to just looking back on their lives at a later date), is considered to be pretty powerful.

They found that having poor relationships with their siblings was more predictive of whether the men would become depressed later in life than having poor relationships with their parents. Here’s a good summary from this piece about the study in the New York Times.

None of the 21 men who had a parent die in childhood became depressed. The 15 percent who had a poor relationship with their mothers and the 16 percent who had a family history of depression suffered depression later in life. But among those who had poor or destructive relationships with siblings, 26 percent had episodes of major depression as adults…The researchers emphasize that their findings do not mean that a poor childhood relationship with a sibling causes depression, but they say the two are strongly associated. Moreover, whether the men’s parents did a good or a poor job of raising them seemed to have little effect on their risk of depression.

…The researchers offered some other examples of how the risks interact. A man whose parents did an average job and who had no family history of depression, but who had a poor relationship with a sibling, would have a 9.9 percent chance of developing depression. But a similar man with a good relationship with at least one sibling would have only a 2.3 percent chance of becoming depressed. In a man with an average parental experience, a family history of depression and poor relationships with siblings, the risk for depression rises to 30 percent.

I don’t think this isn’t what anyone would have expected – probably most people would think that your relationship with your parents would be more important. But there you have it.

You know though, it makes sense, when you think about it. Your parents might “fuck you up,” as Philip Larkin puts it, but your siblings are the only ones on earth who get fucked up the way you do. When the people who share your genes, your experiences, your joys, your traumas, fail to connect with you, it leaves an empty space inside you that nothing can fill.

You can have friends. You can have lovers. But nobody will ever understand why you are who you are the way your siblings do.

You may fight. You may compete. You may even despise each other sometimes. But you’ll never find anyone on earth who could possibly replace them. Sorry if I’m bumming out all the only children out there, but it’s true: this is a bond you’ll just never understand. Siblings are unique.

These are mine, with my dad, a couple of years before I was born:

When I have had schisms with my parents, or with my friends, it has hurt deeply. But when I have had been isolated from my brother and sister it has hurt in a very different way. These two people are closer to me in a way that no one on earth ever could match – only they can begin to understand why I am the way I am, and vice versa. When I do not feel close to them, it feels like a part of me is missing.

Sometimes they make me sad. Sometimes they drive me nuts. Lord knows my brother and I fought like cats and dogs as kids.

But man, am I grateful to have them in my life.