If you find that you have a particular interest in a specific area of study you can certainly write this into your personal statement.
You could consider what it is about the subject that really interests you and provide well-developed specific examples to support this.
You should do your research and make sure that the course you are applying for focuses on the subject area which interests you.
It's important to ensure you keep your interest from being too narrow and try to use several different examples.
We want the personal statement to reflect YOU, what you love and why you love it and indeed why you have chosen to study it.
To read more about writing a personal statement please read our website guidance here.