A licensed clinical psychologist says you can develop a form of PTSD - after your partner has an affair. Dr Kathy Nickerson, 48, revealed a lesser-known condition you can develop after the trauma of your partner cheating on you - called PISD. The condition - which stands for Post Infidelity Stress Disorder - can leave you with PTSD-like symptoms such as anxiety, depression, difficulty sleeping and a constant sense of dread. While it's an informal term rather than an official diagnosis, the condition recognises the long-trauma an affair can inflict on a partner. Dr Kathy, from Orange County, California, said: "When you're in a committed relationship, your partner is the foundation on which so many aspects of your life are built. "When you discover that your partner has cheated, the foundation cracks and you feel as if everything in your life is unsafe, unstable, and insecure. "People are extremely reluctant to talk about infidelity because of the guilt, shame, and judgment they experience when they share their experiences. "As such, most people don't know when their friends or family have been betrayed and were unaware someone was suffering with PISD. "There should be more awareness for PISD and more compassion for both the betrayer and the betrayed." Dr Kathy explained that the condition arises when a person chooses to stay with their partner after being cheated on by them. There are lots of symptoms including feeling depressed, hopeless, anxious, isolated and angry - as well as struggling to sleep and having unusual eating habits. While little-known, Dr Kathy said it can be more common than we realise - because of the trauma a person can go through after being cheated on. She said: "Everything feels wrong because the world as you knew it is shattering, and that is incredibly, incredibly scary and painful. "But many betrayed partners are made to feel foolish, weak, and misguided by well-meaning friends and family when they disclose an affair. "These betrayed partners are very unlikely to share the ongoing pain they are experiencing. Out of fear of more judgment and harassment. "As such, most people don't know when their friends or family have been betrayed and were unaware someone was suffering with PISD." The psychologist and relationship expert said it is possible for a couple to overcome an affair leaving the other partner with PISD. But she explained it's not easy - and takes a lot of effort, time, deep conversation, transparency and reassurance. Dr Kathy, also author of 'The Courage To Stay: How to Heal From an Affair and Save Your Marriage' said: "The most valuable thing a straying partner can do is talk with the hurt partner about their feelings. "They should validate what they hear, and reassure their partner that they're safe now. "The straying partner should also have no further contact with the affair partner and be very transparent about their time, location and communication. "They should then do some deep reflection on why they strayed, so they can make different choices in the future."