Headstand or Sirsasana Pose:
As an upper cervical chiropractor, I get asked if headstands are safe for people's necks all the time. My answer is yes, but with some very important distinctions. The first distinction is that this posture is ALL about how you get into it and how you get out of it. Standing on your head isn't actually the hard part, I promise! What is difficult and can compromise your neck and body is getting up there and getting down. When going into this posture, the most important aspect is that you have a solid base created by your shoulders and forearms. The secret is that you should have almost no actual body weight on the crown of your head. Your body weight is supported by the upper body, not your head and neck, which is why, when done correctly, a headstand is not going to hurt your neck. Coming in and and out of the head stand is all about core engagement so that you are shifting weight appropriately and being sure to protect your neck during this movement.
The health benefits of body inversion are well documented, and done correctly with attention to detail, headstands are beneficial for your body.
So... happy head-standing!