I have been using Vichy Dercos Aminexil products (initially ampoules and for the last two years the foam) for about 8 years (almost a decade now), since the moment I first noticed thinning at the top of my head, which fortunately stopped when I started these treatments. Now I use them regularly but with some breaks, in combination with the corresponding "Vichy Dercos Energising Shampoo Anti-Hair Loss".
It is important to mention that, for acquaintances of mine with significant thinning issues, the same products did not have a notable effect. Thus, I realized that they are suitable only for addressing a problem at its onset. According to my experience, a slight thinning at the beginning can be treated, and the hair gradually thickens.
However, the treatment is not a one-time solution. It needs to be repeated at regular intervals. I found that when I stopped the treatment for a long time, the thinning reappeared.
So, if we are talking about cases that are still at the beginning of the problem, the product does what it promises: it provides strengthening, thus fewer hairs fall out and the hair thickens. When I first used the ampoules, it took three treatments (almost three months) for me to see the first results.
Also, the ampoules are stronger than the foam. If at any point the foam is not effective, we should use the ampoules once or twice and then go back to the foam. As I mentioned before, the result is not permanent; maintenance is required.

I have been using it for about a month in combination with the corresponding shampoo. With 2-3 times a week, I didn't see any drastic difference. Only after each use does it give volume to the hair. Also, the packaging helps because you can take it anywhere.