Cracking or popping your own back often brings about a sense of easier movement and a reduced sense of pain and stiffness. But is it a bad thing to do? From a research perspective, the question does not appear to have been investigated to any great depth. There is research looking into the effect of cracking one's knuckle joints on outcomes such as grip strength, cartilage height and onset of osteoarthritis. I suppose the results of such studies could be applied to the process of cracking one's spinal joints. In short, no one has established any solid links between habitual knuckle cracking and adverse outcomes. The same is probably true for habitual back cracking.
My view is that the question "Is it bad to crack your back?" is probably the wrong question to ask. I think the more pertinent questions are;
Why do you feel the need to habitually crack your back?
How forcefully do you need to twist/move your spine in order to achieve the desired crack / pop feeling?
Why do you feel the need to habitually crack your back?
Usually, people crack their own back to obtain relief of pain and or stiffness in the back. If however, we were able to identify the factor that is driving your desire to habitually crack your back, it may be possible to eliminate the need to do it in the first place. It's possible that your urge to crack your back is driven by a degree of unhelpful distribution of muscular tension. Perhaps you've previously suffered an acute injury and although you've recovered, you're still carrying around a background level of "muscular guarding" that is perpetuating a mild degree of unhelpful compression at particular regions of your spine. This cycle of guarding might be temporarily halted by your habitual back cracking- providing you with a quick and easy, but short lasting relief of symptoms. Perhaps though, the need for this temporary fix could be supplanted by the longer lasting effect of treatment directed at the underlying muscular guarding?
How forcefully do you need to twist/move your spine in order to achieve the desired crack / pop feeling?
In the event that we conclude that there is no particular underlying driver of your felt need to crack your own back, it makes sense for you to simply keep going on doing it so long as it is providing you some benefit. But it is worth considering the questions. 1- How significant are the symptoms that you are keeping at bay by cracking your own back? Again, it may be worth considering a visit to your physio to see if there are other options for longer lasting relief of symptoms. 2- How forcefully do you need to manipulate your own spine in order to get the outcome you want? Despite the fact we don't have research stating that there are adverse effects to cracking your own back, it makes sense to me that the risk of injury (either acute or accumulative) is going to be higher with a more forceful action. Perhaps there is a gentler, lower risk approach for achieving the same sense of movement freedom and pain relief that you gain from cracking your back? The potential for the same outcome with lower risk sounds like a good option to explore, no?
The overall message is that as far as the risk of causing future problems is concerned, habitual back cracking is not necessarily bad thing. I would urge those who have symptoms of pain and stiffness that are significant enough to warrant very frequent, forceful self-manipulation in order to obtain relief to book in with a Physio to have a thorough assessment of the spine.