I sense that mental illness resembles a bone fracture. Bones have remarkable durability, but also, once broken, can rapidly heal and be reset. With normal daily use, one might never be aware of past problems. But a healed bone may or may not be as robust as it was before the break. A vulnerability still remains, the constant potential for a repeat fracture, which is why caution is always necessary.
Depression, and indeed the whole gamut of mental illness, is so varied that generalizations are rarely helpful. It can strike at almost any age, individuals from all walks of life, temperaments and ethnicities. It is no respecter of the divisions that bedevil human society. Sometimes there are obvious causes or triggers; often, there are none at all, its roots perhaps lost in the remotest strata of our genetic inheritance.
Sometimes the affliction disappears as mysteriously as it arrives. It can stop people completely in their tracks, perhaps becoming so acute that it leads to periods of hospitalization. For some, it is mercifully brief; for others, chronic, but somehow compatible with a semblance of normal working life. For me, it has been an ongoing, ever-present consciousness, a constant ache with occasional stabbing pains. I don’t have great highs, though occasionally I envy the thought of them (until I remember that, for friends with the likes of bipolar disorder, these can be just as hard to navigate as the lows).