Not everyone who experiences trauma develops PTSD. PTSD includes a lot of different symptoms from the 3 categories described above, but you may have trauma symptoms without meeting criteria for the diagnosis of PTSD. About 20% of people who have experienced trauma, develop PTSD. Others may experience some symptoms such as anxiety or mood, or intrusive memories, but not as intensely and not as long. The symptoms may resolve with time. PTSD does not tend to resolve with time by itself, it requires treatment.